Y files

Males will not become extinct

Published: Thursday 31 July 2003

reports about the demise of the y chromosome and a consequent extinction of men are exaggerated. This was revealed during the genetic sequencing of the much talked about chromosome.

The male-determining y has long been considered a vestigial chromosome -- a dilapidated repository of genetic material with an ever-dwindling, tiny collection of about 40 genes. The reason for the genetic attrition, scientists thought, was its inability to pair and swap genetic material with any other chromosome. The exchange takes place during a process called crossing-over, which is the key to repair genetic mutations and preserve genes. Because y cannot cross-over, scientists thought all its genes would slowly disappear over time. Controversially, some scientists even believed the genes might all wither away within five million years, and consequently males would become extinct.

But now David Page and his team from the us-based Whitehead Institute for Biomedical Research and Washington University School of Medicine have found that the y chromosome is mightier than thought -- it contains about 78 genes. The researchers discovered that a portion of genes, especially those essential for male fertility, lie in very complex regions of the chromosome that are mirror images of each other and repetitive in nature. This unique arrangement allows the genes to pair up, repairing each other in a process called gene conversion that is similar to crossing-over.

The researchers suggests that the gene conversion is as frequent as crossing over is in regular chromosomes, so much so that a y passed down from father to son will have about 600 base pairs overwritten and hence repaired within one generation.

The work has already increased our understanding about the causes of male infertility. According to the researchers, many men are infertile due to deletions of the mirror image regions.

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