Question

While the HbS allele is the most common variant in West Africa, there are other alleles that confer resistance to malaria. For example, in malaria endemic regions of Southeast Asia, there is another allele, referred to as HbE, which confers malaria resistance to heterozygotes, but has milder health consequences in homozygotes. This variant is fairly common in the population, with allele frequencies up to 25% in some groups, and ____________, suggesting that it has been subjected to positive selective pressure. EXPLAIN.

is in linkage disequilibrium with a larger-than average surrounding region

is found in an average-sized haplotype block

seems to have originated in ancient history

encodes a missense variant

Answer 1

Some researches on malaria in the past decade showed that immunity or resistance against malaria has occurred by the evolution of human genes, which are differently evolved in different geographical areas. For instance, HBB with three different gene coding of single nucleotide polymorphisms (SNPs) created immunity against malaria. The Glu6Val (HbS) allele is common in Africa, Glu6Lys (HbC) allele is frequently seen in West Africa and Glu26Lys (HbE) allele is mostly found in Southeast Asia. These researches confirmed that genes are evolved in the process of immunity, inflammation and cell adhesion which will be a challenge for the scientists of next decade to develop different types of selective vaccines against malaria in different populations with different gene evolutions.

According to recent studies, the Haplotype analysis and statistical model of African and Southeast Asian malaria resistant allele show that this genomic evolution originated in the past 10,000 and 5,000 years respectively.