DNA I | Biology | Visionlearning

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Key experiments are discussed: from Griffith’s discovery of genetic “transformation” to Avery, MacLeod, and McCarty’s determination of the “transforming agent” to confirmation by Hershey and Chase of DNA rather than protein as the genetic material."> <meta name="keywords" content="science, education, STEM, math, biology, chemistry, physics, earth science, online learning"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/biology/2/dna-i/149" }, "name": "DNA I", "headline": "DNA I: The genetic material", "author": { "@type": "Person", "name": "Nathan H Lents, Ph.D." }, "datePublished": "2008-11-01 05:13:33", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_149-23061209063622.png", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "This module is the first in a series that discusses the discovery, structure, and function of DNA. Key experiments are discussed: from Griffith’s discovery of genetic “transformation” to Avery, MacLeod, and McCarty’s determination of the “transforming agent” to confirmation by Hershey and Chase of DNA rather than protein as the genetic material.", "keywords": "science, education, STEM, math, biology, chemistry, physics, earth science, online learning", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2008"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/biology/2/dna-i/149"> <meta property="og:title" content="DNA I | Biology | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="This module is the first in a series that discusses the discovery, structure, and function of DNA. 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<li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/environmental-science/61/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-general-science" data-accordion="button" aria-controls="acc-panel-general-science" aria-expanded="false"> <span class="accordion__button__label"> General Science </span> </button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Biology </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-biological-molecules" data-accordion="button" aria-controls="acc-sub-panel-biological-molecules" aria-expanded="false"> <span class="accordion__button__label"> Biological Molecules </span> </button> <div class="accordion__panel" id="acc-sub-panel-biological-molecules" data-accordion="panel" aria-labelledby="acc-sub-button-biological-molecules" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/carbohydrates/61">Carbohydrates</a></li> <li><a href="/en/library/biology/2/fats-and-proteins/62">Fats and Proteins</a></li> <li><a href="/en/library/biology/2/biological-proteins/243">Biological Proteins</a></li> <li><a href="/en/library/biology/2/blood-biology-i/242">Blood Biology I</a></li> <li><a href="/en/library/biology/2/lipids/207">Lipids</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-cell-biology" data-accordion="button" aria-controls="acc-sub-panel-cell-biology" aria-expanded="false"> <span class="accordion__button__label"> Cell Biology </span> </button> <div class="accordion__panel" id="acc-sub-panel-cell-biology" data-accordion="panel" aria-labelledby="acc-sub-button-cell-biology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/discovery-and-structure-of-cells/64">Discovery and Structure of Cells</a></li> <li><a href="/en/library/biology/2/respiration/285">Respiration</a></li> <li><a href="/en/library/biology/2/membranes-i/198">Membranes I</a></li> <li><a href="/en/library/biology/2/membranes-ii/204">Membranes II</a></li> <li><a href="/en/library/biology/2/cellular-organelles-i/195">Cellular Organelles I</a></li> <li><a href="/en/library/biology/2/cell-division-i/196">Cell Division I</a></li> <li><a href="/en/library/biology/2/cell-division-ii/212">Cell Division II</a></li> <li><a href="/en/library/biology/2/membranes-and-chemical-transport/106">Membranes and Chemical Transport</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-energy-in-living-systems" data-accordion="button" aria-controls="acc-sub-panel-energy-in-living-systems" aria-expanded="false"> <span class="accordion__button__label"> Energy in Living Systems </span> </button> <div class="accordion__panel" id="acc-sub-panel-energy-in-living-systems" data-accordion="panel" aria-labelledby="acc-sub-button-energy-in-living-systems" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/energy-metabolism-i/215">Energy Metabolism I</a></li> <li><a href="/en/library/biology/2/energy-metabolism-ii/225">Energy Metabolism II</a></li> <li><a href="/en/library/biology/2/photosynthesis-i/192">Photosynthesis I</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-evolutionary-biology" data-accordion="button" aria-controls="acc-sub-panel-evolutionary-biology" aria-expanded="false"> <span class="accordion__button__label"> Evolutionary Biology </span> </button> <div class="accordion__panel" id="acc-sub-panel-evolutionary-biology" data-accordion="panel" aria-labelledby="acc-sub-button-evolutionary-biology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/origins-of-life-i/226">Origins of Life I</a></li> <li><a href="/en/library/biology/2/origins-of-life-ii/227">Origins of Life II</a></li> <li><a href="/en/library/biology/2/extinction/295">Extinction</a></li> <li><a href="/en/library/biology/2/mass-extinctions/294">Mass Extinctions</a></li> <li><a href="/en/library/biology/2/charles-darwin-i/110">Charles Darwin I</a></li> <li><a href="/en/library/biology/2/charles-darwin-ii/111">Charles Darwin II</a></li> <li><a href="/en/library/biology/2/charles-darwin-iii/112">Charles Darwin III</a></li> <li><a href="/en/library/biology/2/adaptation/68">Adaptation</a></li> <li><a href="/en/library/biology/2/taxonomy-i/70">Taxonomy I</a></li> <li><a href="/en/library/biology/2/taxonomy-ii/89">Taxonomy II</a></li> <li><a href="/en/library/biology/2/introduction-to-paleoanthropology/258">Introduction to Paleoanthropology</a></li> <li><a href="/en/library/biology/2/the-piltdown-hoax/263">The Piltdown Hoax</a></li> <li><a href="/en/library/biology/2/future-of-human-evolution/259">Future of Human Evolution</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-genetics" data-accordion="button" aria-controls="acc-sub-panel-genetics" aria-expanded="false"> <span class="accordion__button__label"> Genetics </span> </button> <div class="accordion__panel" id="acc-sub-panel-genetics" data-accordion="panel" aria-labelledby="acc-sub-button-genetics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/inheritance/129">Inheritance</a></li> <li><a href="/en/library/biology/2/independent-assortment/145">Independent Assortment</a></li> <li class="current">DNA I</li> <li><a href="/en/library/biology/2/dna-ii/160">DNA II</a></li> <li><a href="/en/library/biology/2/dna-iii/180">DNA III</a></li> <li><a href="/en/library/biology/2/tracking-human-ancestry/248">Tracking Human Ancestry</a></li> <li><a href="/en/library/biology/2/gene-expression/214">Gene Expression</a></li> <li><a href="/en/library/biology/2/population-genetics/249">Population Genetics</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-ecology" data-accordion="button" aria-controls="acc-sub-panel-ecology" aria-expanded="false"> <span class="accordion__button__label"> Ecology </span> </button> <div class="accordion__panel" id="acc-sub-panel-ecology" data-accordion="panel" aria-labelledby="acc-sub-button-ecology" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/biology/2/biodiversity-i/276">Biodiversity I</a></li> <li><a href="/en/library/biology/2/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/biology/2/animal-ecology/283">Animal Ecology</a></li> <li><a href="/en/library/biology/2/biodiversity-ii/281">Biodiversity II</a></li> <li><a href="/en/library/biology/2/animal-behavior/286">Animal Behavior</a></li> <li><a href="/en/library/biology/2/population-biology/287">Population Biology</a></li> <li><a href="/en/library/biology/2/trophic-ecology/293">Trophic Ecology</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Genetics</em></strong> </span> <h1>DNA I: <sub><em>The genetic material</em></sub></h1> <p class="byline">by Nathan H Lents, Ph.D.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/biology/2/dna-i/149/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/biology/2/dna-i/149/quiz">Quiz</a> </li> <li> <a href="/en/library/biology/2/dna-i/149/resources">Teach with this</a> </li> </ul> </nav> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that one of the most important discoveries in biology was made while a British army medical officer was trying to develop a vaccine for pneumonia after World War I? Although a vaccine for pneumonia still does not exist, Frederick Griffith discovered “transformation.” This means that organisms can be genetically reprogrammed into a slightly different version of themselves.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <p><ul class="bulleted"><li>It required numerous experiments by many scientists to determine that DNA, and not protein, is the genetic material on which life is built.</li> <li>DNA can be “transformed,” or genetically re-programmed, into a slightly different version of itself. </li></ul></p> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/cell">cell </a></dt> <dd> the basic structural unit of all living things </dd> <dt><a href="/en/glossary/view/heredity">heredity </a></dt> <dd> the passing of genetic traits from parent to offspring </dd> <dt><a href="/en/glossary/view/strain">strain </a></dt> <dd>(noun) a group of closely related organisms; a distinct variety</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p>Consider yourself. You are an adult human, or nearly so, composed of hundreds of different types of <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>. Each of these cell types has a different structure and function which together make up you as an individual. Millions of <mark class="term" data-term="chemical reaction" data-term-def="A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that&hellip;" data-term-url="/en/glossary/view/chemical+reaction/1547">chemical reactions</mark> are taking place inside these cells, all carefully coordinated and timed. Yet, you started life as one single cell, a <mark class="term" data-term="zygote" data-term-def="A cell that is the result of the combination of two gametes (e.g., a sperm and an egg) and which contains&hellip;" data-term-url="/en/glossary/view/zygote/3766">zygote</mark>, the result of the fusion of a sperm and an egg. How does all this remarkable complexity come about? Just what is it that you inherit that gives you your father's eyes and your mother's hair color? These questions had perplexed scientists and non-scientists alike for thousands of years, and they were addressed through a series of very clever <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> in the early part of the 20th century.</p> <p><section id="toc_1" class=""> <h2>The chemical basis of heredity</h2></p> <p>In the mid-19th century, <mark class="term" data-term="Gregor Mendel" data-term-def="Austrian Augustinian monk and scientist born in Heizendorf (now Hynice, Chech Republic) (1822-1884). In 1865, Mendel wrote <i>Versuche über Pflanzen-Hybride (Treatises&hellip;" data-term-url="/en/glossary/view/Mendel%2C+Gregor/4509">Gregor Mendel</mark> completed his now classic <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> on genetics (see our <a href="/en/library/Biology/2/Mendel-and-Inheritance/129">Mendel and Inheritance</a> module). Mendel proposed that the "characters" that controlled <mark class="term" data-term="inheritance" data-term-def="The transmission of genetic traits from parent to offspring." data-term-url="/en/glossary/view/inheritance/8294">inheritance</mark> exhibited certain patterns of behavior. Specifically, they seemed to operate in pairs and separated independently during reproduction. The work that Mendel did established some trustworthy rules and properties about genetics and <mark class="term" data-term="heredity" data-term-def="The passing of genetic traits from parent to offspring." data-term-url="/en/glossary/view/heredity/8287">heredity</mark>, but no one had any idea what Mendel's "characters" were and how features were passed from <mark class="term" data-term="generation" data-term-def="Offspring at the same step in the line of descent from a common ancestor." data-term-url="/en/glossary/view/generation/8293">generation</mark> to generation. Scientists were convinced that the basis of genetics and heredity could be found somewhere in the chemistry of our <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>.</p><p>In the early 1900s, scientists began to focus on a recently discovered structure in <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> called <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> (named by Walther Flemming from the Greek words for "colored bodies" because they selectively absorbed a red dye that Flemming used to color cells). Curiously, chromosomes seemed to behave in a manner similar to Mendel's "characters." Specifically, they were seen to line up randomly, separate, and then segregate from each other just prior to cell division, reminiscent of Mendel's <mark class="term" data-term="law" data-term-def="In science, a principle that describes a phenomenon, often mathematically." data-term-url="/en/glossary/view/law/8686">laws</mark> of independent assortment and segregation (Figure 1). Gradually, scientists began to suspect a connection between chromosomes and <mark class="term" data-term="heredity" data-term-def="The passing of genetic traits from parent to offspring." data-term-url="/en/glossary/view/heredity/8287">heredity</mark>.</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid149/Image/VLObject-3753-080904100940.jpg" alt="Figure 1: Microscopic view of chromosomes lining up (red circles at top) and separating (red circles at bottom) during mitosis (cell division) in an onion root tip." /> </button> <figcaption> <p><strong>Figure 1</strong>: Microscopic view of chromosomes lining up (red circles at top) and separating (red circles at bottom) during mitosis (cell division) in an onion root tip.</p> </figcaption> </figure> </div> </section> <section id="toc_2"> <h2>DNA or protein?</h2><p>While biologists were becoming convinced that <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> were the physical seat of genetics and <mark class="term" data-term="inheritance" data-term-def="The transmission of genetic traits from parent to offspring." data-term-url="/en/glossary/view/inheritance/8294">inheritance</mark>, chemists were claiming that these structures were made of both <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> and <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark>. So, which was the genetic <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> housing all the hereditary information? Many scientists of the day actually thought it was protein because there are 20 different amino <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark> for building a protein <mark class="term" data-term="polymer" data-term-def="A large molecule consisting of recurring units of a smaller molecule. A polymer can be thought of as a molecular chain,&hellip;" data-term-url="/en/glossary/view/polymer/1593">polymer</mark>, while DNA polymers are made of only four <mark class="term" data-term="nucleotide" data-term-def="The building blocks of DNA and RNA, consisting of a nitrogen base, a five-carbon sugar, and one or more phosphate groups." data-term-url="/en/glossary/view/nucleotide/1603">nucleotide</mark> <mark class="term" data-term="base" data-term-def="Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different&hellip;" data-term-url="/en/glossary/view/base/1574">bases</mark>. </p><p>Consider it this way: The genetic <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> works like a language for storing information consisting of words that are made of individual "letters." The "language" of the <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> <mark class="term" data-term="polymer" data-term-def="A large molecule consisting of recurring units of a smaller molecule. A polymer can be thought of as a molecular chain,&hellip;" data-term-url="/en/glossary/view/polymer/1593">polymer</mark> would only have four different "letters" to work with (the four <mark class="term" data-term="nucleotide" data-term-def="The building blocks of DNA and RNA, consisting of a nitrogen base, a five-carbon sugar, and one or more phosphate groups." data-term-url="/en/glossary/view/nucleotide/1603">nucleotide</mark> bases), while "protein language" would have twenty possible letters – the twenty different amino <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acids</mark>. Imagine making a language using only four letters! Thus, because it offers far more complexity, most scientists in the early 20<sup>th</sup> century believed that <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> was the component of <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> that housed the genetic information. Regarding the DNA, they thought that perhaps it acted as structural support for the chromosomes, like the frame of a house.</p></section> <section id="toc_3"> <h2>Griffith discovers "transformation"</h2><p>Clarification came during the First World War. During the war, hundreds of thousands of servicemen died from pneumonia, a lung infection caused by the bacterium <em>Streptococcus pneumoniae</em>. In the early 1920s, a young British army medical officer named <mark class="term" data-term="Frederick Griffith" data-term-def="(ca. 1879 - 1941) A British microbiologist whose research focused on the epidemiology and pathology of bacterial infectious diseases. In 1928,&hellip;" data-term-url="/en/glossary/view/Griffith%2C+Frederick/5298">Frederick Griffith</mark> began studying <em>Streptococcus pneumoniae</em> in his laboratory in the hopes of developing a <mark class="term" data-term="vaccine" data-term-def="A preparation of a weakened or killed pathogen, such as a bacterium or virus, or of a portion of the pathogen's&hellip;" data-term-url="/en/glossary/view/vaccine/3765">vaccine</mark> against it. As so often happens in scientific <mark class="term" data-term="research" data-term-def="A study or an investigation." data-term-url="/en/glossary/view/research/8257">research</mark>, Griffith never found what he was looking for (there is still no vaccine for pneumonia), but instead, he made one of the most important discoveries in the field of biology: a phenomenon he called "transformation."</p><p>Dr. Griffith had isolated two <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strains</mark> of <em>S. pneumoniae</em>, one of which was pathogenic (meaning it causes sickness or death, in this case, pneumonia), and one which was innocuous or harmless. The pathogenic strain looked smooth under a microscope due to a protective coat surrounding the <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> and so he named this strain <b>S</b>, for smooth. The harmless strain of <em>S. pneumoniae</em> lacked the protective coat and appeared rough under a microscope, so he named it <b>R</b>, for rough (Figure 2).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid149/Image/VLObject-3754-080904100945.jpg" alt="Figure 2: Cartoon depictions of the rough (harmless) and smooth (pathogenic) strains of S. pneumoniae." /> </button> <figcaption> <p><strong>Figure 2</strong>: Cartoon depictions of the rough (harmless) and smooth (pathogenic) strains of <em>S. pneumoniae</em>.</p> </figcaption> </figure> </div> <p>Dr. Griffith observed that if he injected some of the S <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strain</mark> of <em>S. pneumoniae</em> into mice, they would get sick with the symptoms of pneumonia and die, while mice injected with the R strain did not become sick. Next, Griffith noticed that if he applied <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark> to the S strain of <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark>, then injected them into mice, the mice would no longer get sick and die. He thus hypothesized that excessive heat kills the bacteria, something that other scientists, including <mark class="term" data-term="Louis Pasteur" data-term-def="A French chemist and biologist, born in Dole, France (1822-1895). Pasteur founded the science of microbiology and proved that microorganisms cause&hellip;" data-term-url="/en/glossary/view/Pasteur%2C+Louis/4468">Louis Pasteur</mark>, had already shown with other types of bacteria.</p><p>However, Dr. Griffith didn't stop there – he decided to try something: He mixed living R <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> (which are not pathogenic) with heat-killed S bacteria, and then he injected the mixture into mice. Surprisingly, the mice got pneumonia infections and eventually died (Figure 3).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid149/Image/VLObject-3755-080909020939.jpg" alt="Figure 3: Illustration of F. Griffith's discovery of transformation in S. pneumoniae using mice." /> </button> <figcaption> <p><strong>Figure 3</strong>: Illustration of F. Griffith's discovery of transformation in <em>S. pneumoniae</em> using mice.</p> </figcaption> </figure> </div> <p>Dr. Griffith examined samples from these sick mice and saw living S <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark>. This meant that either the S bacteria came back to life, an unlikely scenario, or the live R <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strain</mark> was somehow "transformed" into the S strain. Thus, after repeating this <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark> many times, Dr. Griffith named this phenomenon "transformation." This discovery was significant because it showed that <mark class="term" data-term="organism" data-term-def="Any connected living system, such as an animal, plant, fungus, or bacterium. Organisms may be composed of a single cell or&hellip;" data-term-url="/en/glossary/view/organism/2171">organisms</mark> can somehow be genetically "re-programmed" into a slightly different version of themselves. One strain of bacteria, in this case the R strain of <em>S. pneumoniae</em>, can be changed into something else, presumably because of the transfer of genetic material from a donor, in this case the heat-killed S strain.</p><p>Scientists around the world began repeating this <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark>, but in slightly different ways, trying to discover exactly what was happening. It became clear that, when the S <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> are killed by <mark class="term" data-term="heat" data-term-def="A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures&hellip;" data-term-url="/en/glossary/view/heat/1506">heat</mark>, they break open and many substances are released. Something in this mixture can be absorbed by living bacteria, leading to a genetic transformation. But because the mixture contains <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark>, <mark class="term" data-term="RNA" data-term-def="Ribonucleic acid. A single-stranded nucleic acid containing the sugar ribose. In most organisms, a molecule responsible for transfer of the&hellip;" data-term-url="/en/glossary/view/RNA/1605">RNA</mark>, <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark>, <mark class="term" data-term="lipids" data-term-def="A diverse group of organic molecules that contain long hydrocarbon chains or rings and are hydrophobic. Examples are fats, oils, waxes,&hellip;" data-term-url="/en/glossary/view/lipids/1599">lipids</mark>, and carbohydrates, the question remained – which <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> is the "transforming agent?"</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6806"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The most important finding of Griffith's experiment was that</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6806-0-option-a" name="quiz-option-6806" type="radio" value="organisms can be genetically reprogrammed." > <span class="option__label"> <span class="screen-reader-only">a.</span> organisms can be genetically reprogrammed. </span> </label> <span class="quiz__response" id="response-6806-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6806-1-option-b" name="quiz-option-6806" type="radio" value="heat kills bacteria." > <span class="option__label"> <span class="screen-reader-only">b.</span> heat kills bacteria. </span> </label> <span class="quiz__response" id="response-6806-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_4"> <h2>Avery, MacLeod, and McCarty discover the transforming agent</h2><p>This question was examined in several ways, most famously by three scientists working at The Rockefeller Institute (now Rockefeller University) in New York: <mark class="term" data-term="Oswald Avery" data-term-def="(October 21, 1877 - February 2, 1955) A Canadian-born American physician and medical researcher, considered one of the founders of immunochemistry,&hellip;" data-term-url="/en/glossary/view/Avery%2C+Oswald/5303">Oswald Avery</mark>, <mark class="term" data-term="Colin MacLeod" data-term-def="(January 28, 1909 - February 11, 1972) A Canadian-American geneticist. He received his MD from McGill University in 1932, at the&hellip;" data-term-url="/en/glossary/view/MacLeod%2C+Colin/5296">Colin MacLeod</mark>, and <mark class="term" data-term="Maclyn McCarty" data-term-def="(June 9, 1911 - January 2, 2005) An American physician and geneticist who specialized in infectious diseases. McCarty is remembered for&hellip;" data-term-url="/en/glossary/view/McCarty%2C+Maclyn/5299">Maclyn McCarty</mark>. These scientists did almost exactly what Griffith did in his <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> but with the following changes. First, after heat-killing the S <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strain</mark> of <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark>, the mixture was separated into six test tubes. Thus, each of the test tubes would contain the unknown "transforming agent." A different <mark class="term" data-term="enzyme" data-term-def="Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly&hellip;" data-term-url="/en/glossary/view/enzyme/1595">enzyme</mark> was then added to each tube except one – the <mark class="term" data-term="control" data-term-def="In science, a control is a system for which the expected change or outcome is well known and is measured or&hellip;" data-term-url="/en/glossary/view/control/3801">control</mark> – which received nothing. To the other five tubes, one of the following enzymes was added: RNase, an enzyme that destroys <mark class="term" data-term="RNA" data-term-def="Ribonucleic acid. A single-stranded nucleic acid containing the sugar ribose. In most organisms, a molecule responsible for transfer of the&hellip;" data-term-url="/en/glossary/view/RNA/1605">RNA</mark>; protease, an enzyme that destroys <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark>; DNase, an enzyme that destroys <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark>; lipase, an enzyme that destroys <mark class="term" data-term="lipids" data-term-def="A diverse group of organic molecules that contain long hydrocarbon chains or rings and are hydrophobic. Examples are fats, oils, waxes,&hellip;" data-term-url="/en/glossary/view/lipids/1599">lipids</mark>; or a combination of enzymes that breaks down carbohydrates. </p><p>The <mark class="term" data-term="theory" data-term-def="A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and&hellip;" data-term-url="/en/glossary/view/theory/4854">theory</mark> behind this <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark> was that if the "transforming agent" was, for example, <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> – the transforming agent would be destroyed in the test tube containing protease, but not the others. Thus, whatever the transforming agent was, the <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> in one of the tubes would no longer be able to transform the <em>S. pneumonia</em> <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strains</mark>. When they did this, the result was both dramatic and clear. The liquid from the tubes that received RNase, protease, lipase, and the carbohydrate-digesting <mark class="term" data-term="enzyme" data-term-def="Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly&hellip;" data-term-url="/en/glossary/view/enzyme/1595">enzymes</mark> was still able to transform the R strain of pneumonia into the S strain. However, the liquid that was treated with DNase completely lost the ability to transform the <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> (Figure 4).</p> <div class="figure"> <figure> <button class="lightbox-button lightbox-button--icon" data-lightbox=""> <img src="/img/library/modules/mid149/Image/VLObject-3756-080922120939.jpg" alt="Figure 4: Illustration of the classic experiment by Avery, MacLeod, and McCarty demonstrating that DNA is capable of transforming harmless R strain S. pneumoniae into the pathogenic S strain." /> </button> <figcaption> <p><strong>Figure 4</strong>: Illustration of the classic experiment by Avery, MacLeod, and McCarty demonstrating that DNA is capable of transforming harmless R strain <em>S. pneumoniae</em> into the pathogenic S strain.</p> </figcaption> </figure> </div> <p>Thus, it was apparent that the "transforming agent" in the <mark class="term" data-term="liquid" data-term-def="The state of matter characterized by its condensed nature and ability to flow. Unlike gases, molecules within a liquid often experience&hellip;" data-term-url="/en/glossary/view/liquid/8727">liquid</mark> was <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark>. To further demonstrate this, the scientists took liquid extracted from heat-killed <em>S. pneumoniae</em> (S strain) and subjected it to extensive preparation and purification, isolating only the pure DNA from the mixture. This pure DNA was also able to transform the R <mark class="term" data-term="strain" data-term-def="A group of closely related organisms; a distinct variety, as in a strain of bacteria." data-term-url="/en/glossary/view/strain/8288">strain</mark> into the S strain and generate pathogenic <em>S. pneumoniae</em>. These results provided powerful <mark class="term" data-term="evidence" data-term-def="Support for an idea, opinion, or hypothesis." data-term-url="/en/glossary/view/evidence/8243">evidence</mark> that DNA, and not <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark>, was actually the genetic material inside of living <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6809"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Which agent transformed one strain of bacteria into another?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6809-0-option-a" name="quiz-option-6809" type="radio" value="DNA" > <span class="option__label"> <span class="screen-reader-only">a.</span> DNA </span> </label> <span class="quiz__response" id="response-6809-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6809-1-option-b" name="quiz-option-6809" type="radio" value="RNA" > <span class="option__label"> <span class="screen-reader-only">b.</span> RNA </span> </label> <span class="quiz__response" id="response-6809-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_5"> <h2>Hershey and Chase further investigate <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> vs. protein</h2><p>Despite this very clear result, some scientists remained skeptical and continued to think that <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">proteins</mark> were likely the genetic <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark>. Eight years after the famous Avery, MacLeod, and McCarty <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark> was published, two scientists named <mark class="term" data-term="Alfred Hershey" data-term-def="(December 4, 1908 - May 22, 1997) An American bacteriologist and geneticist. His most famous contribution to science was the Hershey-Chase&hellip;" data-term-url="/en/glossary/view/Hershey%2C+Alfred/5293">Alfred Hershey</mark> and <mark class="term" data-term="Martha Chase" data-term-def="(1927 - August 8, 2003) Also known as Martha C. Epstein, an American geneticist and member of the team whose experiments&hellip;" data-term-url="/en/glossary/view/Chase%2C+Martha/5300">Martha Chase</mark> performed an entirely different type of genetic experiment. For their experimental <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>, they selected an extremely small <mark class="term" data-term="virus" data-term-def="An ultramicroscopic infectious agent that can only replicate within the cells of living hosts, mainly bacteria, plants, and animals. Viruses have&hellip;" data-term-url="/en/glossary/view/virus/5302">virus</mark> called a <mark class="term" data-term="bacteriophage" data-term-def="Any of a group of viruses that infect and reproduce in specific bacteria, usually causing their disintegration or dissolution. After the&hellip;" data-term-url="/en/glossary/view/bacteriophage/5294">bacteriophage</mark> (or just <em>phage</em>), which only infects bacterial <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark>. At that time, scientists knew that when these phage infect a bacterial cell, they somehow "reprogram" the bacterium to transform itself into a factory for producing more phage. They also knew that the phage itself does not enter the bacterium during an infection. Rather, a small amount of material is injected into the <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> and this material must contain all of the information necessary to build more phages. Thus, this injected substance is the genetic material of the phage.</p><p>Hershey and Chase designed a very simple <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiment</mark> to determine which <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark>, <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> or <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark>, acted as the genetic material in phages. To do this, they made use of a technique called radioactive labeling. In radioactive labeling, a radioactive <mark class="term" data-term="isotope" data-term-def="Atoms of the same element with different numbers of neutrons in their atomic nucleus. Isotopes have the same chemical properties and&hellip;" data-term-url="/en/glossary/view/isotope/1516">isotope</mark> of a certain <mark class="term" data-term="atom" data-term-def="The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in&hellip;" data-term-url="/en/glossary/view/atom/1509">atom</mark> is used and can be followed by tracking the <mark class="term" data-term="radioactivity" data-term-def="The spontaneous emission of radiation, due to a nuclear reaction or direct emission from an unstable atomic nucleus. Radioactivity takes&hellip;" data-term-url="/en/glossary/view/radioactivity/5301">radioactivity</mark> (radioactivity is very easily detected by laboratory instruments, even back in the 1940s, and remains a very common tool in scientific research). So, what Hershey and Chase did was to grow two batches of phage in their laboratory. One batch was grown in the presence of radioactive phosphorous. The <mark class="term" data-term="element" data-term-def="One of fewer than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number." data-term-url="/en/glossary/view/element/1510">element</mark> phosphorous is present in large amounts in DNA, but is not present in the proteins of <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> and phage. Thus, this batch of phage would have radio-labeled DNA. The second batch of phage was grown in the presence of radioactive sulfur. Sulfur is an element that is often found in proteins, but never in DNA. Thus, the second batch of phage would have radio-labeled proteins.</p><p>Then, Hershey and Chase used these two batches of phage separately to infect <mark class="term" data-term="bacteria" data-term-def="(plural of bacterium) A large group of one-celled organisms that are found almost everywhere." data-term-url="/en/glossary/view/bacteria/8679">bacteria</mark> and then measured where the <mark class="term" data-term="radioactivity" data-term-def="The spontaneous emission of radiation, due to a nuclear reaction or direct emission from an unstable atomic nucleus. Radioactivity takes&hellip;" data-term-url="/en/glossary/view/radioactivity/5301">radioactivity</mark> ended up. What they observed was that only those bacteria infected by phage with radio-labeled <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> became radioactive, bacteria infected by phage with radio-labeled <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> did not. Thus Hershey and Chase concluded that it is DNA, and not protein, that is injected into the bacteria during phage infection and this DNA must be the genetic material that reprograms the bacteria.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6810"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Hershey and Chase used radioactive phosphorus in their experiment because</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6810-0-option-a" name="quiz-option-6810" type="radio" value="phosphorus is found in the DNA but not proteins of bacteria and phage." > <span class="option__label"> <span class="screen-reader-only">a.</span> phosphorus is found in the DNA but not proteins of bacteria and phage. </span> </label> <span class="quiz__response" id="response-6810-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6810-1-option-b" name="quiz-option-6810" type="radio" value="phosphorus would show up in radio-labeled proteins of phages." > <span class="option__label"> <span class="screen-reader-only">b.</span> phosphorus would show up in radio-labeled proteins of phages. </span> </label> <span class="quiz__response" id="response-6810-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc_6"> <h2>The blueprint of life</h2><p>Taken together, these <mark class="term" data-term="experiment" data-term-def="A test or trial carried out under controlled conditions so that specific actions can be performed and the results can be observed." data-term-url="/en/glossary/view/experiment/8292">experiments</mark> represented strong <mark class="term" data-term="evidence" data-term-def="Support for an idea, opinion, or hypothesis." data-term-url="/en/glossary/view/evidence/8243">evidence</mark> that <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> is the genetic material. Other scientists later confirmed these result in many different kinds of experiments, including showing that <mark class="term" data-term="eukaryotic" data-term-def="Of cells with a nucleus and other organelles that are surrounded by lipid membranes" data-term-url="/en/glossary/view/eukaryotic/6539">eukaryotic</mark>, and even human <mark class="term" data-term="cell" data-term-def="The basic structural unit of all living things." data-term-url="/en/glossary/view/cell/8286">cells</mark> can be "transformed" by the injection of DNA. The result of these findings was to convince the scientific and lay communities that the <mark class="term" data-term="molecule" data-term-def="A particle formed by the chemical bonding of two or more atoms. The molecule is the smallest particle of a&hellip;" data-term-url="/en/glossary/view/molecule/1518">molecule</mark> of <mark class="term" data-term="heredity" data-term-def="The passing of genetic traits from parent to offspring." data-term-url="/en/glossary/view/heredity/8287">heredity</mark> is indeed DNA. It turns out that the initial instincts of many scientists were exactly backward: They assumed that <mark class="term" data-term="protein" data-term-def="Macromolecules that are polymers of individual amino acids arranged in a chain and joined together by peptide bonds (and so also&hellip;" data-term-url="/en/glossary/view/protein/1594">protein</mark> was the genetic material of <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> and DNA merely provided structure. The opposite turned out to be true. The DNA molecule houses genetic information, and proteins act as the structural framework of chromosomes.</p><p>The discovery that <mark class="term" data-term="DNA" data-term-def="Deoxyribonucleic acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding&hellip;" data-term-url="/en/glossary/view/DNA/1604">DNA</mark> was the "transforming agent" and the genetic component of human <mark class="term" data-term="chromosome" data-term-def="The organized genetic structure of DNA with associated proteins that contains the hereditary information necessary for reproduction, protein manufacture, and other functions." data-term-url="/en/glossary/view/chromosome/3760">chromosomes</mark> was one of the greatest discoveries of science in the 20th century. However, the mechanism of how DNA codes for genetic information was initially a complete mystery and became the focus of intense scientific study (see our <a href="/en/library/Biology/2/DNA-II/160">DNA II module</a>). Still today, the study of how DNA functions comprises an entire discipline of science called molecular biology. Originally an offshoot of biochemistry, the field of molecular biology joins biologists, chemists, anthropologists, forensic scientists, geneticists, botanists, and many others who are working to shed light onto the immense complexity of DNA, the so-called <mark class="term" data-term="blueprint" data-term-def="A detailed outline or plan of action. The word technically refers to a process of photographic printing, used chiefly in copying&hellip;" data-term-url="/en/glossary/view/blueprint/5295">blueprint</mark> of life.</p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Nathan H Lents, Ph.D. “DNA I” Visionlearning Vol. BIO (2), 2008. </em> </p>  <div class="title-list" name="further"> <p class="h6 title-list__title"> Further Reading </p> <ul class="grid grid--column-2--md grid--column-3--md gap-1"> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/DNA-II/160"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_160-23061209063635.jpg" alt="DNA II"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> DNA II: <em>The structure of DNA</em> </h2> </div> </article> </a> </li> <li> <a class="no-hover-focus height-100" href="/en/library/Biology/2/DNA-III/180"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_180-23061209063647.jpeg" alt="DNA III"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> DNA III: <em>The replication of DNA</em> </h2> </div> </article> </a> </li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/biology/2/dna-i/149#toc_1">The chemical basis of heredity</a> </li> <li><a href="/en/library/biology/2/dna-i/149#toc_2">DNA or protein?</a> </li> <li><a href="/en/library/biology/2/dna-i/149#toc_3">Griffith discovers "transformation"</a> </li> <li><a href="/en/library/biology/2/dna-i/149#toc_4">Avery, MacLeod, and McCarty discover the transforming agent</a> </li> <li><a href="/en/library/biology/2/dna-i/149#toc_5">Hershey and Chase further investigate DNA vs. protein</a> </li> <li><a href="/en/library/biology/2/dna-i/149#toc_6">The blueprint of life</a> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. 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DNA I | Biology | Visionlearning