5. Sickle Cell Malaria Resistance
Usually, we follow the words "sickle cell" with "anaemia", and images of sick kids will flash across our minds. The mutation for sickle cell anaemia, called HbS, causes the red blood cells to take on a long, curved shape that reduces their ability to carry oxygen and causes severe anaemia. This is obviously bad news, but there is light at the end of the tunnel as sickle cells are generally resistant to malaria. Although severe sickle cell anaemia is caused by the presence of two copies of the HbS mutation, individuals who carry just one copy of the mutation have a higher resistance to malaria, but without the anaemic symptoms as they have enough normal red blood cells to combat the effects of the sickle cells. Unfortunately this mutation still runs the risk of becoming sickle cell anaemia in your offspring if they inherit two copies. There is even more good news though, as a different mutation of the same genes, known as HbC, could make the carrier virtually immune to malaria. Having one copy of the HbC mutation will give you 29% resistance to malaria, but two copies of the mutated gene (the kind that gives you sickle cell anaemia with HbS) will offer a massive 93% higher resistance to malaria with only mild anaemic symptoms. It is thought that this mutation has the potential to spread quickly through communities in which malaria and sickle cell are endemic, as those who inherit the beneficial HbC genes are much more likely to be able to pass them on to their offspring. This really is human evolution at work.