Women win as Y loses out in battle of the Xs

LONDON - Genetic differences between men and women are more extensive and profound than previously believed, according to a study that unravels the complex chemistry of the sexes.

A detailed analysis of the "X" chromosome - the female sex chromosome - has revealed that women are genetically more complicated than men. The findings reveal that men have taken a genetic battering that has diminished the size of their own "Y" sex chromosome.

The battle of the sexes has its roots in a 300-million-year struggle between the X and the Y chromosomes which have vied with each other for influence over successive generations of males and females.

Scientists have now shown that it has been the X chromosome that has retained its physical integrity while the Y chromosome of men has dwindled in size and power to become a mere shadow of its former self.

The first comprehensive survey of the genes that are active on the X chromosome has revealed the dominant position that the female sex chromosome has gained in the long war of attrition with its male counterpart. One consequence is that boys are more prone to genetic diseases than girls.

While the Y chromosome has retained fewer than 100 working genes, the X chromosome contains more than 1000 and is able to deploy them in a more intricate way in women. This has resulted in the female genome becoming very different to that of men, the scientists say.

While women have two X chromosomes, men only have one.

Professor Huntington Willard of Duke University in Durham, North Carolina, one of the leaders of the study published in Nature, said the findings showed that when the X chromosome occurred in women it behaved so differently to when it resided in men that it had effectively resulted in the evolution of another human genome.

- INDEPENDENT