THE MOLECULAR BASIS OF INHERITANCE
GENE MUTATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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harmful
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beneficial
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neutral
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Detailed explanation-1: -It turns out that, in these areas, HbS carriers have been naturally selected, because the trait confers some resistance to malaria. Their red blood cells, containing some abnormal hemoglobin, tend to sickle when they are infected by the malaria parasite.
Detailed explanation-2: -This is because SCD and SCT are an evolutionary trait that people developed in response to help protect them from malaria. As such, this condition is common in large parts of Africa. Symptoms often begin within the first few months of life, but respond well to early, effective treatments.
Detailed explanation-3: -Heterozygotes are therefore more resistant to the debilitating effects of malaria than the normal homozygotes. This heterozygote advantage in many sickle-cell carriers outweighs the severe reproductive disadvantage of the rarer sickle-cell homozygotes.
Detailed explanation-4: -Nearly 90 percent of the world’s SCD population lives in three countries: Nigeria, India, and the Democratic Republic of Congo (figure 1), where the disease affects up to 2 percent of the population, and the carrier prevalence rate (sickle cell trait) is as high as 10 to 30 percent [3, 4, 9, 10].