Why would natural selection not work with turner syndrome?
It does work, just not as obviously as it may seem. Turner Syndrome is caused by a non-disjunction event which leads to a female that is missing part or all of one of her X chromosomes. This is caused by an inefficiency in one of the steps of meiosis. Since meiosis is performed by a large number of proteins and enzymes, Turner syndrome exerts selective pressure on those genes which code for them. Imagine a scenario where a population of individuals had very inefficient meiosis were 1 in 10 girls had Turner syndrome. Then introduce some people that have very efficient meiosis and only 1 in a million girls had Turner syndrome. This new group would have more healthy girls which could in turn continue to pass those good meiosis genes to their children. The other group would use a lot of time and resources on children who could not reproduce (which is a part of Turner). Over time the good meiosis genes would be selected for. Edit: Dana B is mistaken. Those women who have a child with Turner
