Claim CB130:
So-called junk DNA is not really junk. Functions have been found for noncoding DNA which was previously thought to be junk, and we cannot be sure that the rest of the junk DNA is not functional as well.Source:
Behe, Michael J., 2003. A functional pseudogene?: An open letter to
Nature. http://www.arn.org/docs2/news/behepseudogene052003.htm
Response:
- It has long been known that some noncoding DNA has important
functions. (This was known even before the phrase "junk DNA" was
coined.) However, there is good evidence that much DNA has no
function:
- Sections of DNA can be cut out or replaced with randomized sequences with no apparent effect on the organism (Nóbrega et al. 2004).
- Some sections of DNA are corrupted copies of functional coding DNA, but mutations in them, such as stop codons early in the sequence, show that they cannot have retained the same function as the coding copy.
- The fugu fish has a genome that is about one third as large as its close relatives.
- Mutations in functional regions of DNA show evidence of selection -- nonsilent changes occur less often that one would expect by chance. In other sections of DNA, there is no evidence that any changes are selected against.
Links:
EvoWiki, 2004. Junk DNA. http://www.evowiki.org/wiki.phtml?title=Junk_DNAReferences:
- Nóbrega, Marcelo A., Yiwen Zhu, Ingrid Plajzer-Frick, Veena Afzal and Edward M. Rubin, 2004. Megabase deletions of gene deserts result in viable mice. Nature 431: 988-993.
Further Reading:
Knight, J., 2002. Evolutionary genetics: All genomes great and small. Nature 417: 374-376, http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v417/n6887/full/417374a_r.htmlCHI, 2003. DNA glossary. http://www.genomicglossaries.com/content/DNA.asp (registration required)
created 2003-4-19, modified 2004-11-19