Non-coding DNA: Difference between revisions

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The amount of total genomic DNA varies widely between organisms, and the proportion of coding and noncoding DNA within these genomes varies greatly as well. For example, it was originally suggested that over 98% of the [[human genome]] does not encode protein sequences, including most sequences within [[intron]]s and most [[intergenic region|intergenic DNA]],<ref name="Elgar & Vavouri">{{cite journal | vauthors = Elgar G, Vavouri T | title = Tuning in to the signals: noncoding sequence conservation in vertebrate genomes | journal = Trends in Genetics | volume = 24 | issue = 7 | pages = 344–52 | date = July 2008 | pmid = 18514361 | doi = 10.1016/j.tig.2008.04.005 }}</ref> whilst 20% of a typical [[prokaryote]] genome is noncoding.<ref name="Costa non-coding">{{cite book|last1=Costa|first1=Fabrico|editor1-last=Morris|editor1-first=Kevin V.|title=Non-coding RNAs and Epigenetic Regulation of Gene Expression: Drivers of Natural Selection|date=2012|publisher=[[Caister Academic Press]]|isbn=1904455948|chapter=7 Non-coding RNAs, Epigenomics, and Complexity in Human Cells}}</ref>

AccordingIn to some studieseukaryotes, [[genome size]], and by extension the amount of noncoding DNA, is not necessarily correlated to organism complexity, an observation known as the [[C-value paradox]].<ref>{{cite journal |last1=Thomas |first1=C.A. |title=The genetic organization of chromosomes |journal=Annu. Rev. Genet. |date=1971 |volume=5 |page=237–256}}</ref> For example, the genome of the unicellular ''[[Polychaos dubium]]'' (formerly known as ''Amoeba dubia'') has been reported to contain more than 200 times the amount of DNA in humans.<ref name=Gregory>{{cite journal | vauthors = Gregory TR, Hebert PD | title = The modulation of DNA content: proximate causes and ultimate consequences | journal = Genome Research | volume = 9 | issue = 4 | pages = 317–24 | date = April 1999 | pmid = 10207154 | doi = 10.1101/gr.9.4.317 | doi-broken-date = 2017-01-15 }}</ref> The [[pufferfish]] ''[[Takifugu]] rubripes'' genome is only about one eighth the size of the human genome, yet seems to have a comparable number of genes; approximately 90% of the ''Takifugu'' genome is noncoding DNA.<ref name="Elgar & Vavouri"/> Therefore, Themost extensiveof variationthe indifference nuclearin genome size among eukaryotic species is knownnot asdue theto [[C-valuevariation enigma]]in oramount C-valueof paradox.<refcoding name=Wahls>{{cite journal | vauthors = Wahls WPDNA, Wallace LJrather, Mooreit PDis |due title = Hypervariable minisatellite DNA isto a hotspot for homologous recombinationdifference in humanthe cellsamount |of journal = Cell | volume = 60 | issue = 1 | pages = 95–103 | date = January 1990 | pmid = 2295091 | doi = 10.1016/0092non-8674(90)90719-U }}</ref> Most of the genome size difference appears to lie in the noncodingcoding DNA.

In 2013, a new "record" for the most efficient eukaryotic genome was discovered with ''[[Utricularia gibba]]'', a [[bladderwort]] plant that has only 3% noncoding DNA and 97% of coding DNA. Parts of the noncoding DNA were being deleted by the plant and this suggested that noncoding DNA may not be as critical for plants, even though noncoding DNA is useful for humans.<ref name="DesignNTrend" /> Other studies on plants have discovered crucial functions in portions of noncoding DNA that were previously thought to be negligible and have added a new layer to the understanding of gene regulation.<ref>{{cite journal | vauthors = Waterhouse PM, Hellens RP | title = Plant biology: Coding in non-coding RNAs | journal = Nature | volume = 520 | issue = 7545 | pages = 41–2 | date = April 2015 | pmid = 25807488 | doi = 10.1038/nature14378 | bibcode = 2015Natur.520...41W }}</ref>