Junk DNA
"Junk" DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. About 97% of the human genome has been designated as "junk", including most sequences within introns and most intergenic DNA. While much of this sequence may be an evolutionary artifact that serves no present-day purpose, some is believed to function in ways that are not currently understood.
Moreover, the conservation of some junk DNA over many millions of years of evolution may imply an essential function.
8% of human junk DNA has been shown to be formed by retrotransposons of Human Endogenous Retroviruses (HERVs).
Junk DNA may act as a protective buffer against genetic damage and harmful mutations.Junk DNA may have no function.
For example, recent experiments removed 1% of the mouse genome and were unable to detect any effect on the phenotype. This result suggests that the DNA is, in fact, non-functional.
Research Nuggets:
A 2006 study by the McKusick-Nathans Institute of Genetic Medicine (Johns Hopkins) stated that "Junk DNA may not be so junky after all."
Researchers at the University of Illinois Society for Experimental Biology found an antifreeze-protein gene in a species of fish which "evolved" from junk DNA.
A mathematical analysis of the genetic code by IBM identified patterns that suggested junk DNA had an important role after all.
In 2006, University of Iowa researchers documented segments of RNA (previously considered "junk") that regulated protein production, and could generate microRNAs.
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