The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer
In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.
During fertilization, the encounter of gametes results in the fusion of their nuclei. The nucleus of the egg cell thus formed is therefore a mixture of the two nuclei.
So the parent will only give half of his chromosomes, so the child will have 50% of his chromosomes that resemble each of his parents.
Another factor that must be mentioned is the genetic recombination between the chromosomes that occurs during meiosis of the reproductive cells. Thus, this will give a heterogeneous chromosome resulting from recombination of the two chromosomes of each of its parents, and the child will have a unique combination chromosome but keeping the alleles of both parents.
Explanation:
Ocean ridges features form along all types of plate boundaries.
The lower respiratory tract is sometimes referred to as the tracheobronchial tree, this describes the branching structure of airways supplying air to the lungs, this includes the trachea, bronchi and bronchioles.
