Question

Frequency of recombination between linked genes in Drosophila is affected by
A. Distance between genes
B. Sex of heterozygotes for linked genes
C. Age of female
D. Temperature
Choose the correct answer from the options given below:

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

Hint:

While distance is the primary determinant of recombination frequency, remember that it's a biological process, not a fixed physical constant. Therefore, other factors like genetics (sex), physiology (age), and environment (temperature) can modulate the rate of crossing over. The lack of recombination in male Drosophila is a classic exam topic.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Genetic recombination (crossing over) is the process that generates new combinations of alleles on a chromosome. The frequency of this event between two linked genes is not constant and can be influenced by several genetic and environmental factors, particularly in model organisms like Drosophila.
Step 2: Detailed Explanation:
Let's analyze the effect of each factor:


A. Distance between genes: This is the most fundamental factor. According to Sturtevant's principle of gene mapping, the frequency of recombination is directly proportional to the physical distance between the genes on the chromosome. This is correct.

B. Sex of heterozygotes for linked genes: This is a well-known phenomenon in genetics, especially in Drosophila melanogaster. Crossing over and recombination are completely absent in males. Therefore, the sex of the heterozygous parent dramatically affects the outcome. This is correct.

C. Age of female: Studies in Drosophila have shown that the rate of recombination can be influenced by the age of the female fly, generally decreasing as the female gets older. This is correct.

D. Temperature: Temperature is an environmental factor that can influence recombination rates. Exposing flies to temperatures outside their optimal range (either high or low) has been shown to alter the frequency of crossing over. This is correct.

Step 3: Final Answer:
All four listed factors—distance, sex, age, and temperature—are known to affect the frequency of recombination in Drosophila.