Question

Assertion :The maximum frequency of recombination, that can result from crossing over between linked genes, is 50 percent. Reason: Linked genes shown higher frequency of crossing over if distance between them is longer.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Genetic markers located on the same chromosome tend to remain together during sexual reproduction, a phenomenon called linkage. If two genes are completely linked, all gametes would carry the parental combinations and no recombinants would be produced. This in sharp contrast to the 50% recombinant gametes a characteristic of independent assortment. Hence, frequency that can result from crossing over between linked genes is between 0-50%. Strength of the linkage between two genes is inversely proportional to the distance between the two. Linked genes show higher frequency of crossing over if the distance between them is higher and lower frequency if the distance is small. The chance of double or even number of crossovers between them also increases.

So, the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'.