In: Biology
Thalassemia is a genetic disorder where affected individuals have red blood cells that produce too much iron. This disease is inherited as an autosomal recessive (tt). However, heterozygous individuals (carriers= Tt) may have some immunity to malaria (similar to sickle cell anaemia). Human blood samples are obtained from a Mediterranean population of 100 people where malaria is endemic. Of these, 50 people are found to be carriers (Tt), and additional 3 people have thalassemia (tt). Use these observed results to explain if heterozygous individuals have partial immunity to malaria?
No, these results does not indicate that heterozygous individuals i.e. carriers of Thalassemia have partial immunity to malaria. The percentage-wise distribution of genotype of the sample population is as follows : TT : 47%, Tt : 50%, tt : 3%. Whereas there are more people with heterozygotic genotype in the sample, their abundance is not significant enough to suggest that heterozygote genotype is naturally selected in any way. To give an idea, among some African population genotype frequency for Sickle cell heterozygote is as high as 97% and in African - American population it is above 90%. So, clearly heterozygous individuals of this population do not seem to enjoy any sort of immunity to malaria. If heterozygosity provided immunity (from malaria) to its population, natural selection would have greatly favor those with heterozygotic genotype and consequently heterozygote frequency would have been much much more.