9. What does it mean for a trait, such as light skin coloration, to be under gat
ID: 3164690 • Letter: 9
Question
9. What does it mean for a trait, such as light skin coloration, to be under gative selection in equatorial Africa? Relate negative selective pressore lo whar we know about MCIR allele diversity among African populations 10. Why does Dr. Jablonski dismiss the hypothesis that protection from skin cancer provided selection for the evolution of darker skin in our h ancestors? uman 11. Revisit your hypothesis from Question 8. Based on the information you have now, does this seem like a more or less probable hypothesis than when you tirst proposed it? Provide evidence to support your reasoning. Watch the film The Biology of Skin Color minutes. Pause when Dr. Jablonski says, "That is what melanin does." In this segment of the film, Dr. Jablonski references a paper she had r connection between UV exposure and the essential nutrient folate (a B vit which circulates throughout the body in ead obout the tamin) the blood. The paper, published in 1978, ibes how the serum (blood) folate concentrations differed between two groups of light-skinned people.Explanation / Answer
9. Negative selection of a trait occurs when the changes in DNA in which there would be removal of rare alleles that would be deleterious for s population. As a result of this deleterious effect, there would occur a decrease of the negatively selected trait. This type of selection is also referred to as purifying selection or can be called as background selection. As a result of these selections, the deleterious changes in a gene will not be able to take over the population.
The MC1R gene locus is of the melanocortin 1 receptor which is seen to be extremely high in the Africans and and not in Africans. This is because, there is a constraint on the MC1R gene in the environments having high UV B radiations. When the melanocytes stumulating hormone binds to the MC1R, there is a synthesis of black of brown melanin . There is an increased risk of melanoma based on the type of skin. With an increased synthesis in the African populations, it results in decreased chances of melanoma due to such high exposures to UVB in those geographical regions.
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