Question: Do you know anything about genetic disorders and how they affect the body, physically?

Mark Burnley answered on 20 Jun 2011:

One interesting genetic disorder is sickle cell anaemia. In this condition, the red blood cells are often the wrong shape, meaning that they are detected and destroyed by the body. Also, their “sickle shape” means that they have difficulty passing through the capillaries and can sometimes block them. Among many complications with the disease, people with sickle cell anaemia have red blood cell counts that are about half of normal levels, and therefore they would be unable to sustain exercise at normal levels. But there is a benefit. If you only have one of the two sickle cell alleles (you inherit one each from your parents), then the disease is not likely to affect your life but your blood cells lifetime will still be shorter than normal. This is actually a good thing, because the parasite that causes malaria reproduces within the red blood cells, if these cells are destroyed too quickly, they cannot reproduce, and therefore you either won’t catch malaria or you will suffer much milder symptoms. This is probably why sickle cell anaemia has not been “selected out” by evolution: it is an advantage in places where malaria exists.