The correct option is (D).Genetic drift is otherwise known as the Sewall Wright effect or allelic drift and is defined as the change in the allelic frequency of a given population that results due to random sampling
.
Explanation:
Genetic drift refers to a phenomenon that is characterized by the change in the allelic frequency of a given population. It results in the disappearance of the gene variants that eventually leads to a reduction in the genetic variation. Occurrence of chance phenomena like emigration and immigration and independent selection eventually leads to genetic drift. This leads to the increment in the homozygosity as the changes in the associated allelic frequency does not move in the optimum predefined direction. The major driving forces is the genetic mutation or migration apart from random selection. The increased frequency and the fixation of rare alleles also occur due to genetic drift.
Answer: The blood vessels in the umbilical cord, the fetus receives all the necessary nutrition, oxygen, and life support from the mother through the placenta.
