Health

# Brad Pitt + Angelina Jolie = saving the world one baby at a time?

Gene ExpressionBy Razib KhanMar 20, 2006 1:37 AM

Angelina Jolie and Brad Pitt are classic "beautiful people." By now you know they are going to have a baby. What sort of child will this be? Handbag.com offers you a projection:

How many parents would pay to get that extra edge for their child, a notch up the normal distribution?

If life does not begin until late in the pregnancy, then the first trimester could become a gambler's playground and the current ethical conundrums spawned by sex selection might be but the faintest blood in the water. As for Angelina and Brad...being beautiful might just be the grace they get to avoid many of these questions, their faces being manifest advertisements for their health and the reason for their wealth. Addendum: Please note that there is a lot of controversy around many of the terms like "fitness," or the possibility that fitness is heritable (or not). Additionally, though I believe there is a lot of circumstantial evidence for the correlation between beauty and genetic health...it is still circumstantial. 1 - If one of the grandparents has a lethal on a locus, then each viable offspring has a 1/2 chance of carrying that lethal as well. Assuming that the spouses of the siblings don't carry the lethal allele then each grandchild has a 1/4 chance of carrying that particular lethal allele (coefficient of relatedness here is 1/4, so that makes sense). For any two random grandchildren there is a 1/16 chance for a carrier + carrier pairing. 1/4 of the offspring would be inviable. So, multiplying out the independent probability of a 1/16 chance for carrier + carrier matings * 1/4 chance of the lethal combination, you have a 1/64 chance of the lethal reappearing in great-grandchildren assuming a first cousin mating. Or, to be optimistic, a 63/64 chance of the lethal being masked. Pretty good, huh? But what about other loci? The chance are independent, so you would note that as (63/64)^n, as n approaches a higher number the probability of "missing" a hit on all loci starts to drop fast (a "hit" would be a homozygous lethal combination). At 45 loci you reach below 50% expectation of a miss on the all the loci due to first cousin marriages. The numbers for siblings are even more horrendous. And this doesn't take into account that there is another grandparent in the picture...with their own unique bundle of dirty genes.

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