Question

Sickle-cell anemia is frequently described as affecting only Africans or people of African descent; it’s considered a “racial” disease that doesn’t affect other populations. How would you explain to someone that this View is incorrect?

Answer 1

Sickle-cell anaemia follows autosomal recessive pattern oof inheritence from parents, meaning if one parent has sickle-cell anaemia and the other has sickle-cell trait, then the child has a 50% chance of having sickle-cell disease and a 50% chance of having sickle-cell trait. When both parents have sickle-cell trait, a child has a 25% chance of sickle-cell disease, 25% do not carry any sickle-cell alleles, and 50% have the heterozygous condition.

It is frequently described as affecting only Africans or people of African descent because of which it's considered a 'racial' disease that doesn't affect other population. However, this is an icorrect view because as restriction endonuclease analysis, Sickle-cell gene mutation probably arose spontaneously in different geographic areas. The people with sicke cell trait are immune to malaria, since the sickle shaped RBC containg the malarial parasite, Plasmodium ruptures causing its cell cycle to end prematurely. Heterozygotes are still able to contract malaria, but their symptoms are generally less severe. Due to the adaptive advantage of the heterozygote, the disease is still prevalent, especially among people with recent ancestry in malaria-stricken areas, such as Africa, the Mediterranean, India, and the Middle East. Malaria was historically endemic to southern Europe, but it was declared eradicated in the mid-20th century, with the exception of rare sporadic cases.

In the United States, with no endemic malaria, the prevalence of sickle-cell anaemia among African Americans is lower (about 0.25%) than in West Africa (about 4.0%) and is falling. Without endemic malaria, the sickle-cell mutation is purely disadvantageous and tends to decline in the affected population by natural selection, and now artificially through prenatal genetic screening. However, the African American community descends from a significant admixture of several African and non-African ethnic groups and also represents the descendants of survivors of slavery and the slave trade. Thus, a lower degree of endogamy and, particularly, abnormally high health-selective pressure through slavery may be the most plausible explanations for the lower prevalence of sickle-cell anaemia (and, possibly, other genetic diseases) among African Americans compared to West Africans.

This is the reason why sickle-cell anemia is not a racial disease, however due to the selective advantages that the heterozygotes carrying the sickle-cell trait enjoy in regions where malaria is still prevalent such as in Africa, the disease is still flourishing and in regions of USA where, malaria is only sporadic the disease is largly extinct which leads to its appearance as a racial disease.