How do we know that selection is operating at the sickle cell trait?

Question

How do we know that selection is operating at the sickle cell trait?

Answer 1

Genetics is a strange field. To have the sickle cell trait you have to have a black ancestry. To have Tay-Sachs disease you have Jewish ancestry from the Baltic, with that disease you have to have two people with the gene. With Sickle Cell Anemia I think one parent has to have the gene, I'm not sure. I'm not looking this up it comes from studying medicine, no I am not a doctor.

Answer 2

It was noticed that sickle cell was uncommon in the highland areas of West Africa, as the people there don't catch malaria as often. It's common in the lowland areas, with a lot of malaria. So it can be seen that in two very closely related groups the one that has to put up with malaria has to put up with sickle cell too.  It's a trait that's still selected for in malarial areas, as the better part of 1 million children die from malaria every year.

Answer 3

Do you mean natural selection?

Dang. If I hear the word 'sickle cell' again I swear I'll go mad.

Sickle cell anemia is a mutation that causes the blood cells of an individual to mutate from the natural round shape to a sickle shape, hence the name. The sickle cell is naturally resistant to malaria, a parasite that is high contagious and carried by the blood stream.

Though there is a catch. As you know, an individual receives a trait from both of their parents. When the sickle cell trait is passed on it can be heterozygous (one parent) or homozygous (both parents). One parent passing along the trait will result in resistance to malaria, both parents passing along the trait results in a very painful condition, as ALL the blood cells are sickle shaped, which can cause clotting and blocking.

So how is it natural selection? Natural selection is favorable traits being passed on to the next generation, yes? Sickle cell anemia (at least with the one trait) is a very favorable thing to have in African counties because it offers a resistance to malaria. Those with the trait are able to survive malaria, grow up, have babies, and pass the trait on. Voila, natural selection working at a modern day level ^_^

Does that clear things up for you in the very most basic of terms?