Question

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Inbreeding depression is the reduced survival and fertility of offspring of related individuals.
Reason R : Inbreeding increases heterozygosity exposing harmful recessive alleles in homozygotes.

In light of the above statements, choose the correct answer from the options given below:

• A. Both A and R are true and R is the correct explanation of A
• B. Both A and R are true but R is NOT the correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Hint:

Key genetics of inbreeding:
- Inbreeding $\rightarrow$ Increases Homozygosity ($AA$ and $aa$).
- Heterosis/Outbreeding $\rightarrow$ Increases Heterozygosity ($Aa$).
- Depressed vigor is a direct consequence of homozygotization of deleterious recessive alleles.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Inbreeding is the mating of closely related individuals (e.g., selfing, sib-mating).
The genetic consequence of inbreeding is the reorganization of alleles, which alters the frequency of genotypes within the population.

Step 2: Detailed Explanation:
Let us analyze both statements:
Assertion A:
Inbreeding depression is defined as the reduction in fitness, vigor, survival, and fertility of progeny resulting from consecutive generations of inbreeding.
This phenomenon is highly pronounced in cross-pollinated species (e.g., maize, alfalfa) and less pronounced in self-pollinated species.
Thus, Assertion A is true.
Reason R:
The primary genetic effect of inbreeding is that it increases homozygosity and decreases heterozygosity at a rate determined by the closeness of the relationship.
By increasing homozygosity, recessive deleterious alleles that are normally masked in heterozygous state ($Aa$) are brought together in homozygous recessive state ($aa$), where they express their harmful phenotypic effects.
The statement in Reason R states that "Inbreeding increases heterozygosity", which is genetically incorrect because inbreeding reduces heterozygosity.
Thus, Reason R is false.

Step 3: Final Answer:
Assertion A is true, but Reason R is false.
Therefore, the correct option is (C).