Thursday, May 27, 2004

Evolutionary Changes

Genetically, chimpanzees are 98.5 percent identical to humans. But the differences between the species are clearly profound, and geneticists have been laboring to find out how such subtle variations in DNA can be so important.
Fujiyama’s team found that just 1.44 percent of the DNA was different at the level of single letters of genetic code.
Fujiyama’s team found differences that may be more important than the single-letter changes.

“There is also an impressive number (68,000) of small to large stretches of DNA that have been either gained or lost (these are called ’insertions or deletions’, ’indels’ for short) in one species or the other,” the researchers wrote.

“These differences are sufficient to generate changes in most of the proteins: Indeed, 83 percent of the 231 coding sequences, including functionally important genes, show differences at the amino-acid sequence level,” they added.
There is nothing particularly novel about this discovery but it is a cute picture. It has been known since the 60's that DNA coding sequences lead to the production of proteins determined by the sequence of amino acids. Amino acids are determined by DNA 'triplet codons' (3 bases [A,C,T or G] in sequence) and that while changes in the 3rd position (called wobble) are generally tolerated, changes in the 1st or 2nd positions can result in dramatic changes in the amino acid and ultimately the protein produced. Interestingly however, is the fact that when Dubya's DNA was compared to chimp DNA, 99.99999999999999999999999999999% identity was revealed. No doubt an example of 'punctuated equilibrium'.


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6:48 AM  

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