Sunday, November 06, 2011

Battle of the Sexes - ix_a

It seems the mystic questions in the previous post were the outcome of my inability to grasp the knowledge or plain misunderstanding. I said;

Men trying to match up is understandable but why do women try to match down? What are those restrictions at cell level?
Based on the information in the article;
Men must increase gene expression on their lone X-chromosome to match the two X's possessed by women. A new study explains just how men manage to do that.
In mammals, cells therefore work to emphasize, or "upregulate," the lone X-chromosome in males and de-emphasize, or "downregulate," the extra X-chromosome in females.
However, it appears the both male and female X-chromosomes are upregulated (male X-> 2X and females 2X->4X). But females downregulate their upregulaged X-chromosomes (thus 2X same as males). From the new study;
Women have two X chromosomes, while men have one X and one Y. The lack of a 'back up' copy of the X chromosome in males contributes to many disorders that have long been observed to occur more often in males, such as hemophilia, Duchenne muscular dystrophy, and certain types of color blindness. Having only one copy of X and two copies of every other chromosome also creates a more fundamental problem -- with any other chromosome, the gene number imbalance resulting from having only one copy would be lethal. How can males survive with only one X?
Biologists have been debating how organisms and cells manage the imbalance between X and other chromosomes for years, with the dominant theory being that both sexes up-regulate the expression of X-linked genes, essentially doubling their expression to "2X" in males and "4X" in females. Then, to correct the imbalance that now appears in females (since they have the equivalent of "4" Xs now and 2 of every other chromosome), females then 'turn off' one of the hyperactive X chromosomes, resulting in a balanced "2X" expression of those genes across both sexes.
That doesn't lead to philosophical pondeings over the implications. Science sometimes acts as a dampener to imaginatively inclined imbecile.

Via Science Daily

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