Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Morgan observed that the Drosophila genes for yellow body and white eye showed 1.3 percent recombination frequency.
Reason (R): Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes.
In the light of the above statements, choose the most appropriate answer from the options given below:

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

Hint:

- 1% recombination = 1 map unit (centimorgan) - Smaller recombination frequency → genes are closer

Answer 1

The Correct Option is A

Concept: Recombination frequency is used to determine genetic linkage and the distance between genes on a chromosome.

Step 1: Analyze Assertion (A).
Morgan experimentally observed recombination frequencies in Drosophila, including the 1.3% recombination between yellow body and white eye genes. \[ \Rightarrow \text{Assertion is correct} \]

Step 2: Analyze Reason (R).
Sturtevant used recombination frequency to map genes and estimate distances between them on chromosomes. \[ \Rightarrow \text{Reason is correct} \]

Step 3: Link between A and R.
The observation of recombination frequency (A) is explained by the concept that recombination frequency represents gene distance (R).

Step 4: Final conclusion.
Thus: \[ Both A and R are correct and R is the correct explanation of A \]