CINXE.COM

<!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>Higher cells incorporate an ancient chromosome :: DNA from the Beginning</title> <meta name="description" content="Mitochondria contain a circular genome molecule, tightly packed with genes." /> <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 30</span> Higher cells incorporate an ancient 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/30/concept30.jpg"class="concept-image" alt="Higher cells incorporate an ancient chromosome." /> <p>In addition to the set of chromosomes found in the nucleus, a different type of chromosome is found in the energy-generating organelles of the cytoplasm, the mitochondria. The mitochondrial (mt) chromosome contains genes involved in the process of oxidative phosphorylation — the production and storage of energy. There is evidence that mitochondria once existed as free-living bacteria, which were taken up by primitive ancestors of eukaryotic cells. The primitive host cell provided a ready source of energy-rich nutrients, and the mitochondrion provided a means to extract energy using oxygen. This symbiotic relationship became key to survival, as oxygen accumulated in the primitive atmosphere. </p> <p>Mitochondria are physically similar in size to bacteria, and the mt genome retains bacteria-like features. Like bacterial chromosomes, the mt genome is a circular molecule. Also, very few introns are found in mt genes. Plants contain an additional ancient chromosome in the chloroplasts, which were also absorbed as symbionts. </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 href="/29/"><img src="/images/thumbnails/29-thumb-sm.png" alt="29." />DNA is packaged in a chromosome.</a></li> <li ><a class="concept-highlight" 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 = '/30/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>