Question

How do each of these influence genetic diversity (how do they occur/function) (provide true examples or well hypothesised support for each one)

a. mutations

b. gene flow

c. pleiotropy

d. overdominance

Answer 1

Mutations are the most common source of genetic diversity. Evidence of mutations influenced genetic diversity can be observed from the evolutionary traits of animals. Mutations result in the introduction of the new alleles in the population and removal of unwanted traits from the population, thereby making the population more heterogeneous. The best example of the mutation is cancer which is a result of the somatic mutation affecting single cell and that mutation is carried forward to the progeny of cells leading to an uncontrolled growth of cells.

Gene flow is another important mechanism for circulating the genetic diversity among different populations. Migration causes the change in genetic diversity within the populations by changing the allele frequencies. Gene flow refers to the migration of genes between two populations. Gene flow is thus responsible for the observed similarities between the species. Gene flow slows down or may prevent the process of speciation. Therefore gene flow can influence genetic diversity in a particular population but it will keep two populations alike i.e. variations between two populations is less. A classical example of the gene flow induced genetic diversity is of Sika deer. These deer were brought to Western Europe where they reproduced with the native red deer. This external gene flow from the Sika deer resulted in a hybrid population and there are no longer any pure red deer today.

Pleiotropy is yet another factor which directly influences genetic diversity. Pleiotrophy is referred to a condition where one single gene can directly influence more than one phenotypic traits or an individual. Therefore it is obvious that any mutation in this gene will automatically be reflected in the resulting phenotypic traits controlled by the parent gene. The best example of pleiotropy is a human disorder known as phenylketonuria (PKU). It is a genetically inherited disorder that is linked to the increase in the levels of phenylalanine in the body. This disorder is caused by the mutation in the single gene of the chromosome 12 and affects the multiple organ and organ systems of our body.

“Overdominance” can result in a condition where progeny express certain traits that are not demonstrated by either of the parents. The best example of the overdominance influenced genetic variations is sickle cell anemia. In this disease, a change in a single gene or amino acid results in the change in the shape of hemoglobin to sickle-shaped. Heterozygous individuals (Ss) will be normal and will express normal as well as sickle cells, however, homozygous (ss) condition will result in severe disorder and will be life-threatening.