Y chromosome is minimizing its length but will not be extincted !!!

Thursday, May 28, 2009

All chromosomes in the nucleus come in pairs – except the Y chromosome. Each member of a chromosomal pair depends on its mate for genetic repair through sexual recombination. When one half suffers a genetic injury, it can discard the mutated gene and replace it with a normal copy drawn from the other member of the pair. But the Y has no sexual 'partner' with which to swap out defective genes.

However,Researchers from Whitehead Institute for Biomedical Research and Washington University School of Medicine suggested that Y chromosome includes a large number of genes arranged in pairs along this single chromosome in ways that may allow the Y to mimic the paired chromosome structure of the rest of the genome.

"Genes constantly are being bombarded with little injuries – mutations. Mutations can either be beneficial or detrimental, but they are far more often detrimental," said lead researcher David Page. "On the Y, detrimental mutations cannot be discarded."

There's no question that this inability to discard has cost the Y hundreds of genes over time. Many of the chromosome's genes either have weakened or died out altogether. Sexual recombination is a card game the Y just can't win. But this new research suggests it doesn't always need to. For critical genes, it swaps with itself.

Rather than swapping DNA with the X, the Y may exchange DNA with itself, in a recombination process mediated by the palindromes. The palindromes contain genes, so in effect the Y could be able to repair itself, replacing bad sequence with good, suggested by David Page.

"This study shows that the Y chromosome has become very efficient at preserving its important genes," said co-lead investigator Richard K Wilson. "It's found different ways to do the things that chromosomes must do to evolve, survive and thrive."

However, not all scientists r convincened by this! As Mark Jobling points out, the evolutionary cost of this mechanism is very high to occur !!!

reference:

http://genome.wellcome.ac.uk