Question

Part A: The MC1R (melanocortin 1 receptor) gene is responsible for normal pigmentation of skin in humans and controls which kind of melanin is made by skin cells, eumelanin and/or pheomelanin. Melanin serves as a cover for the cells so harmful UV rays cannot reach the nucleus and cause mutation, but also protects folate, a type of B vitamin essential in growth and metabolism. However, there are two sides to this story: exposure to sunlight is required to convert calcium to Vitamin D, an important molecule in bone growth and absorption of essential nutrients.

1. At what latitudes would you expect to find human populations with the highest levels of the two melanin pigments in their skin? Why? Predict the diversity of the MC1R gene in these populations (high/low) and why you might expect this pattern.

2. Would you expect skin color to be plastic? Why or why not?

3. Hypothesize as to why the Inuit (Eskimo) populations have not lost their rather dark skin pigmentation?

Answer 1

The two melanin pigments will be found on the latitudes where UV rays are strongest i.e., where the sun rays are direct and strong. This could be the equator because the sun is closest to it. The MCR1 will be low here because it is responsible for normal pigmentation but at the equator release of pigment Gene is higher which is not normal.

Yes this could be plastic it totally depends on the exposure to the sun. The pigment is generated more when exposed to sun and UV rays. Also possibly it couldn't be because somewhat it depends on genetic inheritance also. If the parents are highly pigmented so will be the children

Eskimos have not lost their pigmentation because they are still exposed to UV rays. The fact is even if the sun is not there , there will be UV rays coming ..and pigmentation is the protection against that.