Question

abnormal hemoglobin that causes sickle cell is an example of a mutation that is:

a)both adaptive in areas without malaria and maladaptive in areas with malaria

b)adaptive in areas with malaria

c)maladaptive in areas with malaria

d)adaptive in areas without malaria

Answer 1

Hemoglobin is an oxygen carrier heme-protein which carries oxygen to different parts of the organ from the lung. Mutation in the hemoglobin protein affects its binding efficiency to the oxygen molecule and lead to compromised oxygen condition in different organs. As a result of mutation, the protein molecules stick to each other and gives a peculiar stiff sickle shape to red blood cells. Sickle cell is a recessive genetic disorder and transferred to progeny from their parents. Homozygous individuals for the mutation have reduced life span whereas heterozygous are normal under standard oxygen conditions but also have reduced oxygen-carrying capacity.

The hemoglobin mutation that causes sickle cell is adaptive in areas with malaria is the right answer. The individual who is heterozygous for sickle cell has resistance to malaria (a disease caused by parasite Plasmodium falciparum). This is because of the unusual shape of red blood cells. The parasite enters the cell and these cells due to their unusual shape send to spleen for elimination and results in removal of the parasite. The sickle cell membrane is porous because of its shape and leads to the leaking of nutrients that parasite requires for its survival and finally dies.

The other options (a, c, d) are not right as the mutation in protein affects the oxygen-carrying capacity which has a negative impact on survival, therefore, it is not adaptive in areas without malaria and in areas with malaria, it gives resistance so it is adaptive.