Question

The recombination frequency between the genes a & c is 5%, b & c is 15%, b & d is 9%, a & b is 20%, c & d is 24% and a & d is 29%. What will be the sequence of these genes on a linear chromosome?

• A. a, d, b, c
• B. d, b, a, c
• C. a, b, c, d
• D. a, c, b, d

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Recombination frequency (RF) is a measure of the distance between genes (1% RF = 1 centimorgan). The relative positions of genes on a chromosome can be mapped using these distances.
Detailed Explanation:
1. Highest distance: a and d (29 units). These are likely at the ends.
2. a and c distance = 5.
3. a and b distance = 20.
4. Since \(a-b (20) + b-d (9) = 29 (a-d)\), the order is \(a \dots b \dots d\).
5. Let's check where \(c\) fits. Distance \(a-c\) is 5, and \(c-b\) should be \(a-b (20) - a-c (5) = 15\).
6. The data given says \(c-b = 15\). This matches.
7. Final sequence: \(a \xrightarrow{5} c \xrightarrow{15} b \xrightarrow{9} d\).
Total distance \(a-d = 5 + 15 + 9 = 29\). Correct.
Distance \(c-d = 15 + 9 = 24\). Correct.
Step 2: Final Answer:
The sequence is a, c, b, d. Option (4) is correct.