Question

Why does inbreeding lead to homozygosity?

Answer 1

Inbreeding is the mating between individuals who are closely related to one another by ancestry. It accumulates superior genes and eliminates less desirable genes. Homozygosity means having two identical alleles of a gene by an organism. Such organisms are called homozygous.

Complete answer:
We know that inbreeding is the mating between individuals of the same breed having common ancestry. It is more likely in smaller populations. Inbreeding helps to accumulate the superior genes from both parents and also eliminating the less desirable genes. The offspring thus produced are superior to both parents.

Although inbreeding helps in producing superior offspring, continuous inbreeding will develop homozygous offspring as it increases the probability of the offspring receiving the same allele of a gene from both parents. This increases the chances of expression of recessive alleles and thus reducing the capability and fitness of offspring. This is called inbreeding depression.

Inbreeding depression is the decrease or loss of fitness and strength of an organism. The mating between the same breeds may lower its ability to reproduce and persist. They may also cause the organism to accumulate recessive or deleterious traits and reduce its fertility and productivity.

Note: Outbreeding is the solution to overcome inbreeding depression. It is the mating between two organisms of different breeds having no common ancestors on either side of the pedigree. Outbreeding is of 3 types-
i) Outcrossing- Mating of animals within the same breed having no common ancestor up to 4-6 generations.
ii) Cross-breeding- Mating between a superior male of one breed and superior female of another breed.
iii) Interspecific Hybridisation- Mating of a male and female of different species.