Question

Let us imagine we take a population and subject it to a programme of inbreeding by mating closely related individuals.

(a) What is likely to happen to the average fitness of individuals initially and why (3 marks)

(b) Let us imagine that all mutations are semi-dominant. What happens to the average fitness if we inbreed and why? (2 marks)

(c) What happens to the average fitness if we continue the programme of inbreeding and why? (4 marks)

Answer 1

(a) Inbreeding results in the increased homozygosity within the offspring populations and generally results in reduced fitness. Inbreeding of closely related species may result in stable offspring generation with little reduced fitness at the initial stages of the experiment conducted. The average fitness of the individuals remain stable at the initial stage due to very little or low reduction in fitness.

(b) Semi dominance or Incomlete dominance occurs when the phenotypic changes are neither a dominant one nor a recessive one but an intermediate one. In this case, if the mutations that are transferred are considered semi dominant, the average fitness will increase and will not lead to inbreeding depression. This is because, the semi dominant state of the mutation will always be featuring an intermediate state of the offspring that will not cause homozygosity or biasness towards expression of recessive genes leading to depression.

(c) If the programme of inbreeding is continued, average fitness is likely to decrease from generation to generation as the level of homozygosity increases . With increase in inbreeding(homozygosity), the mutations and deleterious genes gets accumulated, leading to inbreeding depression and thereby ultimately producing offsprings of abnormalities or making the parent sterile.