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<p><b>Genome size</b> is the total amount of DNA contained within one copy of a genome. It is typically measured in terms of mass in picograms (trillionths (10<sup><font size="2">−12</font></sup>) of a gram, abbreviated pg) or less frequently in Daltons or as the total number of nucleotide base pairs typically in megabases (millions of base pairs, abbreviated Mb or Mbp). One picogram equals 978 megabases.<sup id="cite_ref-Dolezel2003_0-0" class="reference"><font size="2">[1]</font></sup> In diploid organisms, genome size is used interchangeably with the term C-value. An organism's complexity is not directly proportional to its genome size; some single cell organisms have much more DNA than humans (see Junk DNA and C-value enigma).</p>
<h2><span id="Origin_of_the_term" class="mw-headline">Origin of the term</span></h2>
<p>The term "genome size" is often erroneously attributed to Hinegardner<sup id="cite_ref-Hinegardner1976_1-0" class="reference"><font size="2">[2]</font></sup>, even in discussions dealing specifically with terminology in this area of research (e.g., Greilhuber, 2005<sup id="cite_ref-Greilhuber2005_2-0" class="reference"><font size="2">[3]</font></sup>). Notably, Hinegardner<sup id="cite_ref-Hinegardner1976_1-1" class="reference"><font size="2">[2]</font></sup> used the term only once: in the title. The term actually seems to have first appeared in 1968 when Hinegardner wondered, in the last paragraph of his article, whether "cellular DNA content does, in fact, reflect genome size".<sup id="cite_ref-Hinegardner1968_3-0" class="reference"><font size="2">[4]</font></sup> In this context, "genome size" was being used in the sense of genotype to mean the number of genes. In a paper submitted only two months later (in February 1969), Wolf et al. (1969)<sup id="cite_ref-Wolf1969_4-0" class="reference"><font size="2">[5]</font></sup> used the term "genome size" throughout and in its present usage; therefore these authors should probably be credited with originating the term in its modern sense. By the early 1970s, "genome size" was in common usage with its present definition, probably as a result of its inclusion in Susumu Ohno's influential book <i>Evolution by Gene Duplication</i>, published in 1970.<sup id="cite_ref-Ohno1970_5-0" class="reference"><font size="2">[6]</font></sup></p>
<h2><span id="Variation_in_genome_size_and_gene_content" class="mw-headline">Variation in genome size and gene content</span></h2>
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Genome Sizes</div>
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<h3><span id="Further_reading" class="mw-headline">Further reading</span></h3>
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<li><a class="external text" rel="nofollow" href="http://www.chlamydiae.com/docs/Chlamydiales/ev_genomedegradn.asp" rel="nofollow"><font color="#3366bb">Evolution of Chlamydiaceae</font></a></li> <li><span class="citation Journal">Andersson JO Andersson SG (1999). <a class="external text" rel="nofollow" href="http://mbe.oupjournals.org/cgi/content/abstract/16/9/1178" rel="nofollow"><font color="#3366bb">"Genome degradation is an ongoing process in Rickettsia"</font></a>. <i>Molecular Biology and Evolution</i> <b>16</b> (9): 1178–1191. <a class="mw-redirect" title="PubMed Identifier" href="/wiki/PubMed_Identifier"><font color="#0645ad">PMID</font></a> <a class="external text" rel="nofollow" href="http://www.ncbi.nlm.nih.gov/pubmed/10486973" rel="nofollow"><font color="#3366bb">10486973</font></a><span class="printonly">. <a class="external free" rel="nofollow" href="http://mbe.oupjournals.org/cgi/content/abstract/16/9/1178" rel="nofollow"><font color="#3366bb">http://mbe.oupjournals.org/cgi/content/abstract/16/9/1178</font></a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Genome+degradation+is+an+ongoing+process+in+Rickettsia&rft.jtitle=Molecular+Biology+and+Evolution&rft.aulast=Andersson+JO+Andersson+SG&rft.au=Andersson+JO+Andersson+SG&rft.date=1999&rft.volume=16&rft.issue=9&rft.pages=1178%E2%80%931191&rft_id=info:pmid/10486973&rft_id=http%3A%2F%2Fmbe.oupjournals.org%2Fcgi%2Fcontent%2Fabstract%2F16%2F9%2F1178&rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none"> </span></span></li>
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<h2><span id="External_links" class="mw-headline">External links</span></h2>
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<li><a class="external text" rel="nofollow" href="http://www.genomesize.com" rel="nofollow"><font color="#3366bb">Animal Genome Size Database</font></a></li> <li><a class="external text" rel="nofollow" href="http://www.rbgkew.org.uk/cval/homepage.html" rel="nofollow"><font color="#3366bb">Plant DNA C-values Database</font></a></li> <li><a class="external text" rel="nofollow" href="http://www.zbi.ee/fungal-genomesize/index.php" rel="nofollow"><font color="#3366bb">Fungal Genome Size Database</font></a></li> <li><a class="external text" rel="nofollow" href="http://www.cbs.dtu.dk/services/FD/" rel="nofollow"><font color="#3366bb">Fungal Database</font></a> — by CBS</li>
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