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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>Genes come in pairs :: DNA from the Beginning</title> <meta name="description" content="Mendel deduced that pure-bred parents have two copies of the same gene for each trait." /> <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 2</span> Genes come in pairs.</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/2/concept2.jpg" class="concept-image" alt="Genes come in pairs."/> <p>Rather than looking at the pea plant as a whole, Mendel focused on seven individual traits that he could readily distinguish. He found that each trait has two alternate forms. For example, seed color can be green or yellow. By analyzing the results of various crosses, Mendel concluded that each alternative form of a trait is specified by alternative forms of a gene.</p> <p>To follow the inheritance of genes from parent to child, Mendel first needed to be sure which genes each parent carried. Since pea plants are naturally self-fertilizing, "pure-bred" strains were readily available. Each strain contained only one form of the gene that determined a trait. Pure-bred plants with yellow seeds only produced offspring with yellow seeds. Pure-bred plants with green seeds only produced offspring with green seeds. From the results of further experiments, Mendel reasoned that pure-bred plants must have two copies of the same gene for each trait.</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="sections-side sections-side1a" style="padding-top: 56px; margin-top: 3px;"> <li ><a href="/1/"><img src="/images/thumbnails/1-thumb-sm.png" alt="1." />Children resemble their parents.</a></li> <li ><a class="concept-highlight" href="/2/"><img src="/images/thumbnails/2-thumb-sm.png" alt="2." />Genes come in pairs.</a></li> <li ><a href="/3/"><img src="/images/thumbnails/3-thumb-sm.png" alt="3." />Genes don't blend.</a></li> <li ><a href="/4/"><img src="/images/thumbnails/4-thumb-sm.png" alt="4." />Some genes are dominant.</a></li> <li ><a href="/5/"><img src="/images/thumbnails/5-thumb-sm.png" alt="5." />Genetic inheritance follows rules.</a></li> <li ><a href="/6/"><img src="/images/thumbnails/6-thumb-sm.png" alt="6." />Genes are real things.</a></li> <li ><a href="/7/"><img src="/images/thumbnails/7-thumb-sm.png" alt="7." />All cells arise from pre-existing cells.</a></li> <li ><a href="/8/"><img src="/images/thumbnails/8-thumb-sm.png" alt="8." />Sex cells have one set of chromosomes; body cells have two.</a></li> <li ><a href="/9/"><img src="/images/thumbnails/9-thumb-sm.png" alt="9." />Specialized chromosomes determine sex.</a></li> <li ><a href="/10/"><img src="/images/thumbnails/10-thumb-sm.png" alt="10." />Chromosomes carry genes.</a></li> <li ><a href="/11/"><img src="/images/thumbnails/11-thumb-sm.png" alt="11." />Genes get shuffled when chromosomes exchange pieces.</a></li> <li ><a href="/12/"><img src="/images/thumbnails/12-thumb-sm.png" alt="12." />Evolution begins with the inheritance of gene variations.</a></li> <li ><a href="/13/"><img src="/images/thumbnails/13-thumb-sm.png" alt="13." />Mendelian laws apply to human beings.</a></li> <li style="border-bottom: 1px solid #669;"><a href="/14/"><img src="/images/thumbnails/14-thumb-sm.png" alt="14." />Mendelian genetics cannot fully explain human health and behavior.</a></li> </ul> <ul class="menu-side"> <li class="section2"><a href="/15/index.html" title="Molecules of Genetics"><span class="displace">MOLECULES OF GENETICS</span></a></li> <li class="section3" ><a href="/29/index.html" title="Genetic Organization and Control"><span class="displace">GENETIC ORGANIZATION AND CONTROL</span></a></li> </ul> </div> </div>  <br class="clearfloat" /> </div>  <script type="text/javascript"> Event.observe(window, 'load', function() { var uri = '/2/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>