Question

(1) Describe one adaptation that varies across populations. It can be related to variation in population histories of infectious disease exposure, diet, or the environment in which the population lives. (2) Explain the genetic basis for this adaptation. That is, what is the underlying genetic component and what is its function?

Answer 1

One adaptation that varies across populations is Adaptation of human skin color in various populations.

• Skin color variation is one of the most striking examples of human phenotypic diversity.
• It is controled by melanin, a pigmentation located in the base of the epidermis and produced by melanocytes.
• Melanin has two forms, pheomelanin (yellow-reddish) and eumelanin (black-brown).
• the first one is mainly seen in the light-complexioned people and the second is mostly produced in the dark-complexioned people.
• Moreover, the number and size of melanin particles differ among individuals.
• Other skin-related factors are keratin, it is also contribute to skin color variation. ,
• Thus we say, People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin.
• The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades.
• In global populations, skin color is highly reated with latitude.
• It is about the distribution of ultraviolet (UV) radiation.
• Populations closer to the equator line tend to have dark skin for protection against UV (uganda),
• Ooverexposure to UV may decrease folic acid levels and cause skin cancer.
• The lighter skin in populations at higher latitudes is underlying selection to maintain vitamin D photosynthesis, which is a UV-dependent process.

The genetic basis for the skin colour variation and the underlying genetic component and its function are follows

• UV is a driving force for the evolution of human skin colors., understanding the exact genetic mechanism of selection would be crucial to reconstruct human evolutionary history and elucidate the microevolution of adaptive traits.
• explaining a full image of regional skin color adaptation in humans would be challenging because it includes the genes identified to be under selection and these genes could explain phenotypic variation, the interactions and joint effects of genes, and the way they react to the external environments.
• human skin color is a highly variable and complex trait as a consequence of strong selection pressure and is controlled by multiple genetic loci
• Skin color adaptation is a complex process because different populations have shared and independent genetic mechanisms involving a large number of genes with different effect advantages on the phenotype.