I’ve always heard that baldness in males is inherited from their mother’s father. However, I’ve seen plenty of families where the father is bald, the mother’s father has plenty of hair, and the kid is bald. So, what’s the scoop on inheriting baldness? –Debbie Brown, via e-mail
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As you note, popular belief has long held that male baldness is inherited through the mother, and that any lad curious about what’s in store for him hairwise should check out his mom’s father and her paternal uncles. For just as long health-care types have been patiently explaining that this belief is groundless–that instead, as one doctor’s Web site (still) puts it, “a single dominant autosomal gene controls male pattern baldness.” In other words, baldness isn’t a sex-linked characteristic, meaning it’s not transmitted via the X or Y chromosomes that determine whether you’re male or female. Rather it’s passed down via one of the non-sex-linked chromosomes, or autosomes, which are randomly contributed by both parents. So, according to the old theory, you were equally likely to get baldness from either mom or dad.
The researchers, led by Markus Nothen of the University of Bonn, rounded up several hundred balding and nonbalding men and compared their androgen receptor (AR) genes, which are located on the X chromosome. Androgens (male sex hormones) play a key role in balding–castrated men don’t go bald–and the AR gene helps them do their work. The researchers found the balding men were much more likely to have a particular version of the AR gene than the nonbalding men, which they took to mean they’d found a genetic variant that triggers baldness. Nothen and company emphasize that this variant isn’t the sole cause of baldness–other recent research suggests that baldness on your father’s side of the family has something to do with it too. No doubt this helps explain cases of hairy maternal grandpa/bald dad/bald son. But Nothen’s group thinks the mother’s contribution is the principal factor.
