Question

In a mapping study, it was found that two genes- A and B are showing independent assortment. The probable reasons for this independent assortment are-
(A). A and B are not linked
(B). A and B are loosely linked
(C). A and B are located in two different chromosome
(D). A and B are located on the same chromosome but placed far away (\(>\) 50cM) from each other.
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (B), (C) and (D) only.
• C. (A), (C) and (D) only.
• D. (A), (B) and (D) only.

Hint:

Independent assortment (50% recombination) can occur in two ways:
- Genes are on different chromosomes (C).
- Genes are on the same chromosome but very far apart (\(>\) 50 cM) (D).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Independent assortment occurs when alleles of different genes segregate independently of one another during gamete formation, resulting in a recombinant frequency of 50%.

Step 2: Detailed Explanation:
Let us analyze the genetics behind independent assortment:
(A) is correct because independent assortment is the defining genetic characteristic of unlinked genes.
(B) is incorrect because "loosely linked" genes are still physically close enough on the same chromosome to show a recombination frequency of less than 50%.
Although they recombine frequently, they do not show true mathematical independent assortment.
(C) is correct because genes located on different chromosomes assort independently during metaphase I of meiosis, as the alignment of one bivalent does not influence the alignment of another.
(D) is correct because genes located on the same chromosome can assort independently if they are physically far apart (separated by a distance of more than 50 cM).
At this distance, at least one crossover is virtually certain to occur between them during every meiosis, resulting in a 50% recombination frequency that is genetically indistinguishable from being on different chromosomes.
Therefore, statements (A), (C), and (D) are the correct genetic explanations.

Step 3: Final Answer:
This combination corresponds to option (C).