Question

Regarding assertion and reason, choose the correct option.
Assertion[A]: Excessive inbreeding leads to inbreeding depression
Reason[R]: Increased homozygosity leads to loss of heterozygosity

• A. Both A and R are true and R explains A
• B. Both A and R are true but R does not explain A
• C. A is true and R is false
• D. Both A and R are false

Answer 1

The correct option is A Both A and R are true and R explains A

Inbreeding is the breeding of animals that are closely related (siblings) and are allowed to breed for 5 - 6 generations. If a superior male and a female of the same ancestry are mated over prolonged periods of time, it increases homozygosity i.e. the occurrence of the same gene in both the pairs of chromosomes of the individual. This helps us in creating a pure line of the animal whose progeny would all be as superior if not more than their parents. As a consequence of increased homozygosity, a phenomenon called loss of heterozygosity also occurs. Now this same concept could be applied to inferior genes or harmful disease causing recessive genes. When the individuals were heterozygous, the recessive allele was masked by the normal allele thereby ensuring that the animal was healthy and not prone to disease. But with the loss of heterozygosity in subsequent generations, individuals might end up with both copies of the recessive gene thereby making the individual more prone to disease. Therefore, when inbreeding occurs excessively, the progeny suffer from what is called inbreeding depression.