The sickle-cell allele is well-known as a mutation that causes red blood cells to deform into a sickle shape when deoxygenated in AS heterozygotes, where A represents the non-mutant version of the -globin gene, and also confers malaria resistance in AS heterozygotes.
MDR-TB refers to TB bacteria that are resistant to two of the most significant TB medications, isoniazid (INH) and rifampicin (R).
Extensively drug-resistant tuberculosis (XDR-TB) occurs when an individual develops MDR-TB that is resistant to additional medications such as fluoroquinolones and injectables.
The CCR5-delta 32 mutation effectively closes "the door," preventing HIV from entering the cell. Only 1% of Northern Europeans, notably Swedes, are resistant to HIV infection.
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