An individual who is heterozygous in regard to hemoglobin type 's' (which can lead to sickle shaped blood cells) and type 'a' (which supports a round shape) will probably Have ancestors from Alaska or the northernmost part of the Americas Be somewhat protected against malaria and be healthy enough to reproduce Die of Malaria Die of Sickle Cell Anemia Have no children
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Step 1: The individual is heterozygous for the sickle cell trait, meaning they have one copy of the normal hemoglobin gene (A) and one copy of the sickle cell gene (S). Show more…
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A person who is heterozygous for the sickle cell and normal hemoglobin alleles usually does not have symptoms of sickle cell anemia, so in this respect they are like a person who is homozygous for the normal hemoglobin allele. This is why textbooks usually describe the sickle cell allele as recessive. However, people who are heterozygous for the sickle cell allele are not exactly like people who are homozygous for the normal hemoglobin allele. People who are heterozygous for the sickle cell allele are less likely to develop severe malaria, an infection of the red blood cells which is transmitted by mosquitoes in many tropical countries. Thus, in areas where malaria is widespread, people who are heterozygous for the sickle cell allele are less likely to become seriously ill and die. Because of this advantage, the sickle cell allele became relatively common in regions like West Africa where malaria is common. Since African-Americans are descended from populations in which the sickle cell allele was relatively common, African-Americans have relatively high rates of the sickle cell allele (approximately 8% are heterozygous for this allele and 0.16% are homozygous). 1. Suppose that a person who is heterozygous for the sickle cell allele (Hh) marries a person who is also heterozygous for this allele (Hh). Draw a Punnett Square to show the expected genetic makeup of their children. On average, what fraction of their children will suffer from sickle cell anemia? On average, what fraction of their children will be heterozygous for the sickle cell allele? (These children will not have sickle cell anemia and will be less likely to develop severe malaria.)
Adi S.
In humans, sickle cell anemia is caused by a mutation in a hemoglobin gene. This mutation affects the red blood cell shape, but it also affects oxygen-carrying ability and resistance to malaria. This gene is best described as: incompletely dominant pleiotropic imprinted or epigenetic polygenic
Shveta P.
In humans, one of the genes for the hemoglobin protein can become mutated in a manner that produces sickle-shaped red blood cells. If two copies of the mutant (recessive) allele are inherited, the individual develops sickle-cell anemia. As you learned in previous lectures, the allele is much more frequent in populations where the risk of malaria is high, as heterozygous individuals do not readily develop anemia or malaria. A: Assume that, in a population of humans in Africa, the sickle-cell allele has a frequency of 15%, while the dominant (normal) hemoglobin allele has a frequency of 85%. If malaria became increasingly more prevalent, would you expect the frequency of the sickle-cell allele to ever become more frequent in the population than the dominant allele? Explain your response.
Joanna Q.
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