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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>DNA is packaged in a chromosome :: DNA from the Beginning</title> <meta name="description" content="Each chromosome is a package for one very long, continuous strand of DNA." /> <link rel="preload" as="style" src="/css/main.css"> <link rel="preload" as="script" src="/js/swfobject.js"> <link rel="preload" as="script" src="/js/prototype-1.6.1.js"> <link href="/css/main.css" rel="stylesheet" type="text/css" /> <link href='https://fonts.googleapis.com/css?family=Droid+Serif' rel='stylesheet' type='text/css'/> <link href='https://fonts.googleapis.com/css?family=Droid+Sans' rel='stylesheet' type='text/css'/> <script type="text/javascript" src="/js/swfobject.js"></script> <script type="text/javascript" src="/js/prototype-1.6.1.js"></script> </head> <body> <div id="container"> <div id="content"> <div id="header"> <div class="rollover-home"> <a href="/" class="rollover-home" title="DNA from the Beginning Home"><span class="displace">Home</span></a> </div> </div>  <div id="content-container"> <h1><span> Concept 29</span> DNA is packaged in a chromosome.</h1> <div id="nav"> <ul> <li class="menu1"><a href="index.html" title="CONCEPT" ><span class="displace">CONCEPT</span></a></li> <li class="menu2"><a href="animation.html" title="ANIMATION"><span class="displace">ANIMATION</span></a></li> <li class="menu3"><a href="gallery.html" title="GALLERY"><span class="displace">GALLERY</span></a></li> <li class="menu4"><a href="av.html" title="VIDEO"><span class="displace">VIDEO</span></a></li> <li class="menu5"><a href="bio.html" title="BIO"><span class="displace">BIO</span></a></li> <li class="menu6"><a href="problem.html" title="PROBLEM"><span class="displace">PROBLEM</span></a></li> <li class="menu7"><a href="links.html" title="LINKS" ><span class="displace">LINKS</span></a></li> </ul> <br class="clearfloat" /> </div> <div id="concept"> <img src="/images/29/concept29.jpg" class="concept-image" alt="DNA is packaged in a chromosome." /> <p>Work on cytology in the late 1800s had shown that each living thing has a characteristic set of chromosomes in the nucleus of each cell. During the same period, biochemical studies indicated that the nuclear materials that make up the chromosomes are composed of DNA and proteins. In the first four decades of the 20th century, many scientists believed that protein carried the genetic code, and DNA was merely a supporting "scaffold."</p> <p> Just the opposite proved to be true. Work by Avery and Hershey, in the 1940s and 1950s, proved that DNA is the genetic molecule. Work done in the 1960s and 1970s showed that each chromosome is essentially a package for one very long, continuous strand of the DNA. In higher organisms, structural proteins, some of which are histones, provide a scaffold upon which DNA is built into a compact chromosome. The DNA strand is wound around histone cores, which, in turn, are looped and fixed to specific regions of the chromosome. </p> </div> </div> <br class="clearfloat" /> <div id="footer"> <ul> <li><a href="/">Home</a></li> <li><a href="/sitemap.html">Site Map</a></li> <li><a href="/scientists.html">Scientists</a></li> <li><a href="/glossary.html">Glossary</a></li> <li><a href="/feedback.html">Feedback</a></li> <li><a href="/awards.html">Awards</a></li> <li><a href="/credits.html">Credits</a></li> <li><a href="http://blogs.dnalc.org/dnaftb/" style="background-image:none;">Blog</a></li> </ul> <p> Funded by <a href="http://macyfoundation.org">The Josiah Macy, Jr. Foundation</a><br /> © 2002 - 2011, <a href="http://www.dnalc.org/"> DNA Learning Center</a>, <a href="https://www.cshl.edu/">Cold Spring Harbor Laboratory</a>. All rights reserved. </p> </div>  </div> <div id="sidebar"> <div id="search" > <form method="get" action="/search"> <div class="fieldHolder1"> <input type="search" id="q" name="q" placeholder="Search" onclick="this.value=''" value="" /> <img style="background-color:#9C0;" src="/images/general/search_icon.jpg" alt="Search" onclick="document.forms[0].submit()" /> </div> </form> </div>  <div id="sidebar"> <ul class="menu-side" > <li class="section1"><a href="/1/index.html" title="Classical Genetics"><span class="displace">CLASSICAL GENETICS</span></a></li> <li class="section2" style="margin-bottom: 3px;"><a href="/15/index.html" title="Molecules of Genetics"><span class="displace">MOLECULES OF GENETICS</span></a></li>  </ul> <ul class="sections-side sections-side3a" style="padding-top: 56px;" > <li ><a class="concept-highlight" href="/29/"><img src="/images/thumbnails/29-thumb-sm.png" alt="29." />DNA is packaged in a chromosome.</a></li> <li ><a href="/30/"><img src="/images/thumbnails/30-thumb-sm.png" alt="30." />Higher cells incorporate an ancient chromosome.</a></li> <li ><a href="/31/"><img src="/images/thumbnails/31-thumb-sm.png" alt="31." />Some DNA does not encode protein.</a></li> <li ><a href="/32/"><img src="/images/thumbnails/32-thumb-sm.png" alt="32." />Some DNA can jump.</a></li> <li ><a href="/33/"><img src="/images/thumbnails/33-thumb-sm.png" alt="33." />Genes can be turned on and off.</a></li> <li ><a href="/34/"><img src="/images/thumbnails/34-thumb-sm.png" alt="34." />Genes can be moved between species.</a></li> <li ><a href="/35/"><img src="/images/thumbnails/35-thumb-sm.png" alt="35." />DNA responds to signals from outside the cell.</a></li> <li ><a href="/36/"><img src="/images/thumbnails/36-thumb-sm.png" alt="36." />Different genes are active in different kinds of cells.</a></li> <li ><a href="/37/"><img src="/images/thumbnails/37-thumb-sm.png" alt="37." />Master genes control basic body plans.</a></li> <li ><a href="/38/"><img src="/images/thumbnails/38-thumb-sm.png" alt="38." />Development balances cell growth and death.</a></li> <li ><a href="/39/"><img src="/images/thumbnails/39-thumb-sm.png" alt="39." />A genome is an entire set of genes.</a></li> <li ><a href="/40/"><img src="/images/thumbnails/40-thumb-sm.png" alt="40." />Living things share common genes.</a></li> <li style="border-bottom: 1px solid #669;"><a href="/41/"><img src="/images/thumbnails/41-thumb-sm.png" alt="41." />DNA is only the beginning for understanding the human genome.</a></li> </ul> </div>  </div>  <br class="clearfloat" /> </div>  <script type="text/javascript"> Event.observe(window, 'load', function() { var uri = '/29/index.html'; uri = uri.replace(/-\d/,''); $('nav').down().descendants().each(function(s) { if (s.nodeName == 'A') { if (s.href.match(uri)) { s.addClassName('current'); throw $break; } } }); }); </script> <script type="text/javascript"> var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-1818773-10']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = 'https://www.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); </script>  <script async src="https://www.googletagmanager.com/gtag/js?id=G-K6EHFCRJBP"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-K6EHFCRJBP'); </script> </body> </html>