Y chromosome: The price you pay when you do not buy.


The current issue of the Science publishes three papers (http://www.sciencemag.org/content/343/6170/536.abstract; http://www.sciencemag.org/content/343/6170/541.abstract;

http://www.sciencemag.org/content/343/6170/544.abstract

) that discuss the exposure of the opposite sex on life span or aging. In C. elegans, not only the copulation but also the exposure of hermaphrodites to medium in which males were once present can induce shortening of the life span of hermaphrodites. The same observation was made independently in Drosophila in which female-produced pheromones have negative effect on longevity of males.

It looks interesting to me because C. elegans has no Y chromosome whereas Drosophila has. Both organisms balanced the expression of sex chromosome linked genes by the dosage compensation mechanism. In C. elegans, the rate of transcription is down regulated from both X chromosomes in hermaphrodites. In male Drosophila, the rate of transcription increases by two folds for the X chromosome. This is needed because there are no or few active genes on the Y chromosome due to degeneration. This makes us to think that one day we will be with out the Y chromosome like C. elegans.  However, these recently published papers forced me to think a putative link between the Y chromosome and longevity. It might be that the presence of the Y chromosome makes female more selective for masculine characters. Killing of males with the Y chromosome allows female to restrict the male-defining genes in a small group that are selected to mate in next generation. Similarly, in the absence of the Y chromosome, killing of hermaphrodite allows to restrict the superior female genes in a small group that will be selected for contributing to next generation. In the absence of the Y chromosome, even the environment becomes a killer.

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