Wednesday, May 16, 2007

Something On Genome Wide Repeats


Was readin up on chromosome organisation in Watson. Something came to my mind. Two things actually.

Transposon Dating: How rare are human transposition events? Can those sequences, which are relics of transposition events found in the genome-wide-repeat subset of the intergenetic DNA, be used for phylogenetic analysis ?

Gene Pool Hypothesis: DNA sequences in the genome wide repeat subset of the intergenetic zone are thought to be relics of transposition events. They play no functional role in the species with respect to lending their DNA as an expression template. Can one expect the evolutionary pressures to be relaxed on these zones relative to actual protein coding/regulatory genetic zones? If so, then could this rich pool of variable DNA sequences serve as a birth place of novel genes. A genetic nebula. Such novel genes, if they exist at all and are discovered would be expected to bear little homology to other pre-existing genes.

If a tree based on sequence homology for all the 27000 human genes is constructed what would it look like?
1.What is the kind of homology amongst these 27000 genes?

2.Out of them how many would have a true common single ancestral gene and how many would have formed independently of this ancestral root? Or how many roots can account for the entire human gene repertoire?

3.Would these independently formed nodes in this tree be good places to look for genes which makes humans more so than say other primates?

4.Have any of the above independently formed genes been derived from mutation in the transposition-events relics found in the genome-wide-repeat zones in the intergenetic DNA (discussed previously) ?

5.Can the above mentioned zones give rise to sequences coding for trans-regulatory-RNA apart from or if not full-fledged genes?

If any of the above 2 mechanisms are real then some of the complexity of humans can be ascribed to the above gene forming pools of the junk DNA component of the human genome.

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