By Delia K. Cabe
I f a book about the human Y chromosome were to make the best-seller list, it might be titled The Masculine Mystique. Like a biological counterpart to Betty Friedan's The Feminine Mystique, the book would explore the genesis of maleness. Some of its themes might even echo Friedan's classic: sexual identity, evolution and self-expression. But as the story of Y unfolds, the book would read more like a mystery, a murky tale that reveals long-held secrets about a diminutive protagonist who veers toward degeneracy.
Not that our central character is powerless. After all, Y can take credit for about half the human population. (The other half are, of course, women.) But when it comes to chromosome allocation, there is no equality of the sexes.
Consider this: Women carry 23 pairs of chromosomes, each set matched like a new pair of socks. In females, the 23rd pair is an XX. Males carry 23 sets also, but their 23rd pair is an XY twosomeone sock and its severely frayed partner, the Y chromosome, which is actually an X cropped at one end. The maimed chromosome has only 20 or 30 genes compared with roughly 2,000 to 3,000 genes on the mighty X.
Scientists identified the X and Y chromosomes at the turn of the last century. Not until 1959, however, did they realize that Y carries the code for maleness. Having discovered the male chromosomal headquarters, they could now figure men outor so they thought. During the ensuing manhunt for maleness genes, which began in earnest in the 1980s, scientists sought to answer a handful of questions. How did the Y come to be? Might the source of male infertility lie hidden within it? Are X and Y related? Which genes on the Y chromosome instigate diseases?
Then came a map to guide researchers through the wilds of the human Y. Published in 1992, the rough map showed the chromosome's genetic landmarks, which would help scientists pinpoint the locations of genes. The map emerged from the laboratory of HHMI investigator David C. Page, a seasoned veteran of Y chromosome research at MIT's Whitehead Institute for Biomedical Research. Now, Page and his lab team are about to release the next chapter in the book of Y: The completion of a map of all the DNA on Y.
Reprinted from the September 2000 HHMI Bulletin, Vol. 13, No. 3,