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  • DNA in the News

    Women's X chromosome unique, analysis reveals

    Last Updated Thu, 17 Mar 2005 14:26:33 EST
    CBC News

    LONDON - A woman's X chromosome is more complex than a man's, making more of certain proteins that could explain some gender differences, a study suggests.

    For the first time, an international team of researchers have sequenced more than 99 per cent of the gene-containing regions of the human X chromosome.

    The new analysis suggests that people owe their sex in part to chromosomes that evolved nearly 300 million years ago in a genderless organism.

    Huntington Willard of Duke University and Laura Carrel of Pennsylvania State University, who analyzed genes on the X chromosome, share their findings in Thursday's issue of the journal Nature.

    In a second study in the same issue, the international team reports finding 1,098 genes on the X chromosome, which amounts to about four per cent of the human genome.

    Humans have 23 pairs of chromosomes. Females have two X chromosomes; males have one X and one much smaller Y.

    The new studies show the Y has less than 100 genes encoding proteins that maintain human tissues.

    With the analysis in hand, researchers can now explore genetic sources of conditions like testicular cancer, as well as hemophilia and Duchenne muscular dystrophy that are more common in males.

    Until now, researchers thought the X and Y shared a common ancestry since they are known to swap small sections during cell division.

    It's thought that changes to one of a pair of non-sex chromosomes in a genderless organism led male features to develop and the Y chromosome to take on its smaller size.

    The new sequence has revealed 43 more genes that are suspected to play a role in several conditions, such as cleft palate and some forms of blindness.