View source for What is genome size?

<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">&minus;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).</p>
<p>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 &quot;genome size&quot; 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 &quot;cellular DNA content does, in fact, reflect genome size&quot;.<sup id="cite_ref-Hinegardner1968_3-0" class="reference"><font size="2">[4]</font></sup> In this context, &quot;genome size&quot; 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 &quot;genome size&quot; 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, &quot;genome size&quot; 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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[[File:Genome Sizes.png|thumb]]Genome Sizes Abizar</div>
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<p>The genome sizes of thousands of eukaryotes have been analyzed over the past 50 years, and these data are available in online databases for animals, plants, and fungi (see external links). Nuclear genome size is typically measured in eukaryotes using either densitometric measurements of Feulgen-stained nuclei (previously using specialized densitometers, now more commonly using computerized image analysis<sup id="cite_ref-Hardie2002_6-0" class="reference"><font size="2">[7]</font></sup>) or flow cytometry. In prokaryotes, pulsed-field gel electrophoresis and complete genome sequencing are the predominant methods of genome size determination. Nuclear genome sizes are well known to vary enormously among eukaryotic species. In animals they range more than 3,300-fold, and in land plants they differ by a factor of about 1,000.<sup id="cite_ref-Bennett2005_7-0" class="reference"><font size="2">[8]</font></sup><sup id="cite_ref-Gregory2005_8-0" class="reference"><font size="2">[9]</font></sup> Protist genomes have been reported to vary more than 300,000-fold in size, but the high end of this range (<i>Amoeba</i>) has been called into question. In eukaryotes (but not prokaryotes), variation in genome size is not proportional to the number of genes, an observation that was deemed wholly counterintuitive before the discovery of non-coding DNA and which became known as the C-value paradox as a result. However, although there is no longer any paradoxical aspect to the discrepancy between genome size and gene number, this term remains in common usage. For reasons of conceptual clarification, the various puzzles that remain with regard to genome size variation instead have been suggested by one author to more accurately comprise a puzzle or an enigma (the C-value enigma). Genome size correlates with a range of features at the cell and organism levels, including cell size, cell division rate, and, depending on the taxon, body size, metabolic rate, developmental rate, organ complexity, geographical distribution, and/or extinction risk (for recent reviews, see Bennett and Leitch 2005<sup id="cite_ref-Bennett2005_7-1" class="reference"><font size="2">[8]</font></sup>; Gregory 2005<sup id="cite_ref-Gregory2005_8-1" class="reference"><font size="2">[9]</font></sup>). Based on completely sequenced genome data currently (as of April 2009) available, log-transformed gene number forms a linear correlation with log-transformed genome size in bacteria, archea, viruses, and organelles combined whereas a nonlinear (semi-natural log) correlation in eukaryotes (Hou and Lin 2009 <sup id="cite_ref-Hou2009_9-0" class="reference"><font size="2">[10]</font></sup>). The nonlinear correlation for eukaryotes, although claim of its existence contrasts the previous view that no correlation exists for this group of organisms, reflects disproportinately fast increasing noncoding DNA in increasingly large eukaryotic genomes. Although sequenced genome data are practically biased toward small genomes, which may compromise the accuracy of the empirically derived correlation, and the ultimate proof of the correlation remains to be obtained by sequencing some of the largest eukaryotic genomes, current data do not seem to rule out a correlation.</p>
<h2><span id="Genome_reduction" class="mw-headline">Genome reduction</span></h2>
<p><b>Genome reduction</b>, also known as <b>Genome degradation</b>, is the process by which a genome shrinks relative to its ancestor. Genomes fluctuate in size regularly, especially in Bacteria, but in some situations a genome has drastically lost content during some period.</p>
<p>The most evolutionary significant cases of genome reduction may be the eukaryotic organelles that are derived from bacteria: the mitochondrion and plastid. These organelles are descended from endosymbionts, which can only survive within the host cell and which the host cell likewise needs for survival. Many mitochondria have less than 20 genes in their entire genome, whereas a free-living bacterium generally has at least 1000 genes. Many genes have been transferred to the host nucleus, while others have simply been lost and their function replaced by host processes.</p>
<p>Other bacteria have become endosymbionts or obligate intracellular pathogens and experienced extensive genome reduction as a result. This process seems to be dominated by genetic drift resulting from small population size, low recombination rates, and high mutation rates, as opposed to selection for smaller genomes.</p>
<p>Some free-living marine bacterioplanktons also shows signs of genome reduction, which are hypothesized to be driven by natural selection.<sup id="cite_ref-Dufresne2005_10-0" class="reference"><font size="2">[11]</font></sup><sup id="cite_ref-Giovannoni2005_11-0" class="reference"><font size="2">[12]</font></sup><sup id="cite_ref-Giovannoni2008_12-0" class="reference"><font size="2">[13]</font></sup></p>
<h3><span id="Genome_reduction_in_obligate_endosymbiotic_species" class="mw-headline">Genome reduction in obligate endosymbiotic species</span></h3>
<p><b>Obligate endosymbiotic species</b> are characterized by a complete inability to survive external to their <b>host</b> environment. These species have become a considerable threat to human health, as they are often highly capable of evading human immune systems and manipulating the host environment to acquire nutrients. A common explanation for these keen manipulative abilities is the <b>compact</b> and <b>efficient</b> genomic structure consistently found in obligate endosymbionts. This compact genome structure is the result of massive losses of extraneous DNA - an occurrence that is exclusively associated with the loss of a free-living stage. In fact, as much as 90% of the genetic material can be lost when a species makes the evolutionary transition from a <b>free-living</b> to <b>obligate intracellular</b> lifestyle. Common examples of species with reduced genomes include: <i>Buchnera aphidicola</i>, <i>Rickettsia prowazekii</i> and <i>Mycobacterium leprae</i>. One obligate endosymbiont of psyllid, <i>Candidatus Carsonella ruddii</i>, has the smallest genome currently known among cellular organisms at 160kb.<sup id="cite_ref-Nakabachi2006_13-0" class="reference"><font size="2">[14]</font></sup> It is important to note, however, that some obligate intracellular species have positive fitness effects on their hosts. (See also mutualists and parasites.)</p>
<p>The <b>reductive evolution model</b> has been proposed as an effort to define the genomic commonalities seen in all obligate endosymbionts.<sup id="cite_ref-Wernegreen2005_14-0" class="reference"><font size="2">[15]</font></sup> This model illustrates four general features of reduced genomes and obligate intracellular species:</p>
<ol>
    <li>&lsquo;genome streamlining&rsquo; resulting from relaxed selection on genes that are superfluous in the intracellular environment;</li>
    <li>a bias towards deletions (rather than insertions), which heavily affects genes that have been disrupted by accumulation of mutations (pseudogenes)<sup id="cite_ref-Moran2004_15-0" class="reference"><font size="2">[16]</font></sup>;</li>
    <li>very little or no capability for acquiring new DNA; and</li>
    <li>considerable reduction of effective population size in endosymbiotic populations, particularly in species that rely on vertical transmission.</li>
</ol>
<p>Based on this model, it is clear that endosymbionts face different adaptive challenges than free-living species.</p>
<h2><span id="Conversion_from_picograms_.28pg.29_to_base_pairs_.28bp.29" class="mw-headline">Conversion from picograms (pg) to base pairs (bp)</span></h2>
<div class="rellink relarticle mainarticle">Main article: C-value</div>
<dl><dd></dd></dl>
<p>&nbsp;&nbsp;&nbsp;[[File:Pico gram to basepair eq.png]]</p>
<p>or simply:</p>
<dl><dd><span class="texhtml"><font face="바탕">1pg = 978Mb</font></span><sup id="cite_ref-Dolezel2003_0-1" class="reference"><font size="2">[1]</font></sup></dd></dl>
<h2><span id="See_also" class="mw-headline">See also</span></h2>
<ul>
    <li>Comparison of different genome sizes</li>
    <li>Animal Genome Size Database</li>
    <li>Cell nucleus</li>
    <li>Comparative genomics</li>
    <li>C-value</li>
    <li>C-value enigma</li>
    <li>Genome</li>
    <li>Human genome</li>
    <li>Junk DNA</li>
    <li>Noncoding DNA</li>
    <li>Plant DNA C-values Database</li>
    <li>Selfish DNA</li>
    <li>Transposable elements</li>
</ul>
<h2><span id="References" class="mw-headline">References</span></h2>
<div style="column-count: 2; -moz-column-count: 2; -webkit-column-count: 2" class="references-small references-column-count references-column-count-2">
<ol class="references">
    <li id="cite_note-Dolezel2003-0">^ <sup><i><b><font size="2">a</font></b></i></sup> <sup><i><b><font size="2">b</font></b></i></sup> <span class="citation Journal">Dolezel J, Barto&scaron; J, Voglmayr H, Greilhuber J (2003). &quot;Nuclear DNA content and genome size of trout and human&quot;. <i>Cytometry A</i> <b>51</b> (2): 127&ndash;128. doi:10.1002/cyto.a.10013. PMID&nbsp;12541287.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Nuclear+DNA+content+and+genome+size+of+trout+and+human&amp;rft.jtitle=Cytometry+A&amp;rft.aulast=Dolezel+J%2C+Barto%C5%A1+J%2C+Voglmayr+H%2C+Greilhuber+J&amp;rft.au=Dolezel+J%2C+Barto%C5%A1+J%2C+Voglmayr+H%2C+Greilhuber+J&amp;rft.date=2003&amp;rft.volume=51&amp;rft.issue=2&amp;rft.pages=127%E2%80%93128&amp;rft_id=info:doi/10.1002%2Fcyto.a.10013&amp;rft_id=info:pmid/12541287&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Hinegardner1976-1">^ <sup><i><b><font size="2">a</font></b></i></sup> <sup><i><b><font size="2">b</font></b></i></sup> <span class="citation book">Hinegardner R (1976). &quot;Evolution of genome size&quot;. In F.J. Ayala. <i>Molecular Evolution</i>. Sinauer Associates, Inc., Sunderland. pp.&nbsp;179&ndash;199.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=bookitem&amp;rft.btitle=Evolution+of+genome+size&amp;rft.atitle=Molecular+Evolution&amp;rft.aulast=Hinegardner+R&amp;rft.au=Hinegardner+R&amp;rft.date=1976&amp;rft.pages=pp.%26nbsp%3B179%E2%80%93199&amp;rft.pub=Sinauer+Associates%2C+Inc.%2C+Sunderland&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Greilhuber2005-2"><b>^</b> <span class="citation Journal">Greilhuber J, Doležel J, Lys&aacute;k M, Bennett MD (2005). &quot;The origin, evolution and proposed stabilization of the terms 'genome size' and 'C-value' to describe nuclear DNA contents&quot;. <i>Annals of Botany</i> <b>95</b> (1): 255&ndash;260. doi:10.1093/aob/mci019. PMID&nbsp;15596473.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=The+origin%2C+evolution+and+proposed+stabilization+of+the+terms+%27genome+size%27+and+%27C-value%27+to+describe+nuclear+DNA+contents&amp;rft.jtitle=Annals+of+Botany&amp;rft.aulast=Greilhuber+J%2C+Dole%C5%BEel+J%2C+Lys%C3%A1k+M%2C+Bennett+MD&amp;rft.au=Greilhuber+J%2C+Dole%C5%BEel+J%2C+Lys%C3%A1k+M%2C+Bennett+MD&amp;rft.date=2005&amp;rft.volume=95&amp;rft.issue=1&amp;rft.pages=255%E2%80%93260&amp;rft_id=info:doi/10.1093%2Faob%2Fmci019&amp;rft_id=info:pmid/15596473&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Hinegardner1968-3"><b>^</b> <span class="citation Journal">Hinegardner R (1968). &quot;Evolution of cellular DNA content in teleost fishes&quot;. <i>American Naturalist</i> <b>102</b>: 517&ndash;523. doi:10.1086/282564.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Evolution+of+cellular+DNA+content+in+teleost+fishes&amp;rft.jtitle=American+Naturalist&amp;rft.aulast=Hinegardner+R&amp;rft.au=Hinegardner+R&amp;rft.date=1968&amp;rft.volume=102&amp;rft.pages=517%E2%80%93523&amp;rft_id=info:doi/10.1086%2F282564&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Wolf1969-4"><b>^</b> <span class="citation Journal">Wolf U, Ritter H, Atkin NB, Ohno S (1969). &quot;Polyploidization in the fish family Cyprinidae, Order Cypriniformes. I. DNA-content and chromosome sets in various species of Cyprinidae&quot;. <i>Humangenetik</i> <b>7</b> (3): 240&ndash;244. PMID&nbsp;5800705.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Polyploidization+in+the+fish+family+Cyprinidae%2C+Order+Cypriniformes.+I.+DNA-content+and+chromosome+sets+in+various+species+of+Cyprinidae&amp;rft.jtitle=Humangenetik&amp;rft.aulast=Wolf+U%2C+Ritter+H%2C+Atkin+NB%2C+Ohno+S&amp;rft.au=Wolf+U%2C+Ritter+H%2C+Atkin+NB%2C+Ohno+S&amp;rft.date=1969&amp;rft.volume=7&amp;rft.issue=3&amp;rft.pages=240%E2%80%93244&amp;rft_id=info:pmid/5800705&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Ohno1970-5"><b>^</b> <span class="citation book">Ohno S (1970). <i>Evolution by Gene Duplication</i>. New York: Springer-Verlag. ISBN&nbsp;0045750157.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=book&amp;rft.btitle=Evolution+by+Gene+Duplication&amp;rft.aulast=Ohno+S&amp;rft.au=Ohno+S&amp;rft.date=1970&amp;rft.place=New+York&amp;rft.pub=Springer-Verlag&amp;rft.isbn=0045750157&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Hardie2002-6"><b>^</b> <span class="citation Journal">Hardie DC, Gregory TR, Hebert PDN (2002). &quot;From pixels to picograms: a beginners' guide to genome quantification by Feulgen image analysis densitometry&quot;. <i>Journal of Histochemistry and Cytochemistry</i> <b>50</b> (6): 735&ndash;749. PMID&nbsp;12019291.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=From+pixels+to+picograms%3A+a+beginners%27+guide+to+genome+quantification+by+Feulgen+image+analysis+densitometry&amp;rft.jtitle=Journal+of+Histochemistry+and+Cytochemistry&amp;rft.aulast=Hardie+DC%2C+Gregory+TR%2C+Hebert+PDN&amp;rft.au=Hardie+DC%2C+Gregory+TR%2C+Hebert+PDN&amp;rft.date=2002&amp;rft.volume=50&amp;rft.issue=6&amp;rft.pages=735%E2%80%93749&amp;rft_id=info:pmid/12019291&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Bennett2005-7">^ <sup><i><b><font size="2">a</font></b></i></sup> <sup><i><b><font size="2">b</font></b></i></sup> <span class="citation book">Bennett MD, Leitch IJ (2005). &quot;Genome size evolution in plants&quot;. In T.R. Gregory. <i>The Evolution of the Genome</i>. San Diego: Elsevier. pp.&nbsp;89&ndash;162.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=bookitem&amp;rft.btitle=Genome+size+evolution+in+plants&amp;rft.atitle=%5B%5BThe+Evolution+of+the+Genome%5D%5D&amp;rft.aulast=Bennett+MD%2C+Leitch+IJ&amp;rft.au=Bennett+MD%2C+Leitch+IJ&amp;rft.date=2005&amp;rft.pages=pp.%26nbsp%3B89%E2%80%93162&amp;rft.place=San+Diego&amp;rft.pub=Elsevier&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Gregory2005-8">^ <sup><i><b><font size="2">a</font></b></i></sup> <sup><i><b><font size="2">b</font></b></i></sup> <span class="citation book">Gregory TR (2005). &quot;Genome size evolution in animals&quot;. In T.R. Gregory. <i>The Evolution of the Genome</i>. San Diego: Elsevier. pp.&nbsp;3&ndash;87.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&amp;rft.genre=bookitem&amp;rft.btitle=Genome+size+evolution+in+animals&amp;rft.atitle=%5B%5BThe+Evolution+of+the+Genome%5D%5D&amp;rft.aulast=Gregory+TR&amp;rft.au=Gregory+TR&amp;rft.date=2005&amp;rft.pages=pp.%26nbsp%3B3%E2%80%9387&amp;rft.place=San+Diego&amp;rft.pub=Elsevier&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Hou2009-9"><b>^</b> <span class="citation Journal">Hou Y, Lin S (2009). &quot;Distinct Gene Number- Genome Size Relationships for Eukaryotes and Non-Eukaryotes: Gene Content Estimation for Dinoflagellate Genomes&quot;. <i>PLoS ONE</i> <b>4</b> (9): e6978.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Distinct+Gene+Number-+Genome+Size+Relationships+for+Eukaryotes+and+Non-Eukaryotes%3A+Gene+Content+Estimation+for+Dinoflagellate+Genomes&amp;rft.jtitle=PLoS+ONE&amp;rft.aulast=Hou+Y%2C+Lin+S&amp;rft.au=Hou+Y%2C+Lin+S&amp;rft.date=2009&amp;rft.volume=4&amp;rft.issue=9&amp;rft.pages=e6978&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Dufresne2005-10"><b>^</b> <span class="citation Journal">Dufresne A, Garczarek L, Partensky F (2005). &quot;Accelerated evolution associated with genome reduction in a free-living prokaryote&quot;. <i>Genome Biol</i> <b>6</b>: R14.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Accelerated+evolution+associated+with+genome+reduction+in+a+free-living+prokaryote&amp;rft.jtitle=Genome+Biol&amp;rft.aulast=Dufresne+A%2C+Garczarek+L%2C+Partensky+F&amp;rft.au=Dufresne+A%2C+Garczarek+L%2C+Partensky+F&amp;rft.date=2005&amp;rft.volume=6&amp;rft.pages=R14&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Giovannoni2005-11"><b>^</b> <span class="citation Journal">Giovannoni SJ, et al. (2005). &quot;Genome streamlining in a cosmopolitan oceanic bacterium&quot;. <i>Science</i> <b>309</b> (5738): 1242&ndash;1245. doi:10.1126/science.1114057. PMID&nbsp;16109880.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Genome+streamlining+in+a+cosmopolitan+oceanic+bacterium&amp;rft.jtitle=Science&amp;rft.aulast=Giovannoni+SJ%2C+et+al.&amp;rft.au=Giovannoni+SJ%2C+et+al.&amp;rft.date=2005&amp;rft.volume=309&amp;rft.issue=5738&amp;rft.pages=1242%E2%80%931245&amp;rft_id=info:doi/10.1126%2Fscience.1114057&amp;rft_id=info:pmid/16109880&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Giovannoni2008-12"><b>^</b> <span class="citation Journal">Giovannoni SJ, et al. (2008). &quot;The small genome of an abundant coastal ocean methylotroph&quot;. <i>Environmental Microbiology</i> <b>10</b> (7): 1771&ndash;1782. doi:10.1111/j.1462-2920.2008.01598.x. PMID&nbsp;18393994.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=The+small+genome+of+an+abundant+coastal+ocean+methylotroph&amp;rft.jtitle=Environmental+Microbiology&amp;rft.aulast=Giovannoni+SJ%2C+et+al.&amp;rft.au=Giovannoni+SJ%2C+et+al.&amp;rft.date=2008&amp;rft.volume=10&amp;rft.issue=7&amp;rft.pages=1771%E2%80%931782&amp;rft_id=info:doi/10.1111%2Fj.1462-2920.2008.01598.x&amp;rft_id=info:pmid/18393994&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Nakabachi2006-13"><b>^</b> <span class="citation Journal">Nakabachi A, et al. (2006). &quot;The 160-kilobase genome of the bacterial endosymbiont <i>Carsonella</i>&quot;. <i>Science</i> <b>314</b>: 267&ndash;267. doi:10.1126/science.1134196.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=The+160-kilobase+genome+of+the+bacterial+endosymbiont+%27%27Carsonella%27%27&amp;rft.jtitle=Science&amp;rft.aulast=Nakabachi+A%2C+et+al.&amp;rft.au=Nakabachi+A%2C+et+al.&amp;rft.date=2006&amp;rft.volume=314&amp;rft.pages=267%E2%80%93267&amp;rft_id=info:doi/10.1126%2Fscience.1134196&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Wernegreen2005-14"><b>^</b> <span class="citation Journal">Wernegreen J (2005). &quot;For better or worse: Genomic consequences of genomic mutualism and parasitism&quot; (PDF). <i>Current Opinion in Genetics and Development</i> <b>15</b>: 1&ndash;12<span class="printonly">. http://journals2005.pasteur.ac.ir/COGD/15(6).pdf#page=10</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=For+better+or+worse%3A+Genomic+consequences+of+genomic+mutualism+and+parasitism&amp;rft.jtitle=Current+Opinion+in+Genetics+and+Development&amp;rft.aulast=Wernegreen+J&amp;rft.au=Wernegreen+J&amp;rft.date=2005&amp;rft.volume=15&amp;rft.pages=1%E2%80%9312&amp;rft_id=http%3A%2F%2Fjournals2005.pasteur.ac.ir%2FCOGD%2F15%286%29.pdf%23page%3D10&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
    <li id="cite_note-Moran2004-15"><b>^</b> <span class="citation Journal">Moran NA, Plague GR (2004). &quot;Genomic changes following host restriction in bacteria&quot;. <i>Current Opinion in Genetics &amp; Development</i> <b>14</b>: 627&ndash;633. doi:10.1016/j.gde.2004.09.003.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Genomic+changes+following+host+restriction+in+bacteria&amp;rft.jtitle=Current+Opinion+in+Genetics+%26+Development&amp;rft.aulast=Moran+NA%2C+Plague+GR&amp;rft.au=Moran+NA%2C+Plague+GR&amp;rft.date=2004&amp;rft.volume=14&amp;rft.pages=627%E2%80%93633&amp;rft_id=info:doi/10.1016%2Fj.gde.2004.09.003&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
</ol>
</div>
<h3><span id="Further_reading" class="mw-headline">Further reading</span></h3>
<ul>
    <li><a class="external text" rel="nofollow" href="http://www.chlamydiae.com/docs/Chlamydiales/ev_genomedegradn.asp"><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"><font color="#3366bb">&quot;Genome degradation is an ongoing process in Rickettsia&quot;</font></a>. <i>Molecular Biology and Evolution</i> <b>16</b> (9): 1178&ndash;1191. <a class="mw-redirect" title="PubMed Identifier" href="/wiki/PubMed_Identifier"><font color="#0645ad">PMID</font></a>&nbsp;<a class="external text" rel="nofollow" href="http://www.ncbi.nlm.nih.gov/pubmed/10486973"><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"><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&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=article&amp;rft.atitle=Genome+degradation+is+an+ongoing+process+in+Rickettsia&amp;rft.jtitle=Molecular+Biology+and+Evolution&amp;rft.aulast=Andersson+JO+Andersson+SG&amp;rft.au=Andersson+JO+Andersson+SG&amp;rft.date=1999&amp;rft.volume=16&amp;rft.issue=9&amp;rft.pages=1178%E2%80%931191&amp;rft_id=info:pmid/10486973&amp;rft_id=http%3A%2F%2Fmbe.oupjournals.org%2Fcgi%2Fcontent%2Fabstract%2F16%2F9%2F1178&amp;rfr_id=info:sid/en.wikipedia.org:Genome_size"><span style="display: none">&nbsp;</span></span></li>
</ul>
<h2><span id="External_links" class="mw-headline">External links</span></h2>
<ul>
    <li><a class="external text" rel="nofollow" href="http://www.genomesize.com"><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"><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"><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/"><font color="#3366bb">Fungal Database</font></a> &mdash; by CBS</li>
</ul>