We may be headed for an all-female future civilization. For one simple reason: Women have two X chromosomes, while men have only one. For the most part, this isn't a problem. But now it seems that this genetic setup could lead to a scenario where the elimination of one key protein could wipe out all men on the face of the planet, but leave women perfectly healthy. Or so a group of researchers says.
In certain respects, men and women are like fruit flies. They differentiate their genders through a paired set of chromosomes. Double X chromosomes mean that the baby fly's clothes should all be a powder pink. An X chromosome paired up with a Y chromosome means that the baby fly can be pressured by his father to be an eagle scout. The same goes for humans. Two Xs make a girl. An X and a Y make a boy.
The problem is, there is some important stuff on the X chromosome and while girls' Xes work as a team, a boy's single X has to struggle through alone. This means that some health conditions caused by defective X chromosomes are almost unknown in girls. If something's wrong in a gene on one X chromosome, the other can step up. If a boy gets an X with a problem, there is no back-up.
Even in healthy males, the lack of an extra X may pose a problem. Genes can't just sit around looking pretty. They have to be expressed; to form a functional product. There's a whole mechanism that goes into taking the information on a piece of DNA and turning it into, say, a hand. If that mechanism is weak the human, or fly, it belongs to is in big trouble. In humans and flies, males only have one X that can be expressed, half the number that females do.
Scientists have suspected that males had a certain protein that increased the expression of the X chromosome, but the increase was thought to be small. Recently some researchers totaled up the expression of the X chromosome, compared to the other chromosomes, in male fruit flies. They found that the protein just about doubled the expression of the chromosome. Given the magnitude of the change in expression, the researchers believe that suppression of this protein could be the reason many medical conditions are found more commonly in men than they are in women.
The protein is called MSL, which sounds innocuous. It stands for Male-Specific Lethal, which emphatically does not sound innocuous. Without this protein, the males would die. Although it has only been studied in flies, researchers think that it works in human males just the way it works in fruit flies. If there were a way to completely suppress it, all men (And women, I think. And flies.) would be in a great deal of trouble.
Via Live Science.