Question

What will be the recombination frequency between the 2 gene (a and b), if the linkage map of X-chromosomes of Drosophila has 66 units with yellow body gene (a) at one end and bobbed hair gene (b) at another end?
A) Less than or equal to 50%
B) Exact 66%
C) Greater than 50%
D) Exact 100%

Answer 1

Hint: Recombinant frequency is a frequency which has a single chromosomal crossover that will take place between the two genes during the meiosis. It is the good estimation of the real distance between the genes.

Complete Answer:
- Recombination frequency is directly proportional to the distance between the genes. They are used for the linkage map preparation. It can be defined as the measurement of the linkage of genetic material in a gene map.
- There is a centimorgan which is a unit which describes that the recombination frequency has a map unit of 1%.
- This type of linear relationship holds true for lower values only but for the recombination frequency beyond 50%, the linear relationship will not follow.
- The recombination frequency is always less than the mapping distance and can never go beyond 50%.
- If the linkage map of X-chromosomes of Drosophila has 66 units with yellow body gene (a) at one end and bobbed hair gene (b) at another end then their recombination frequency will be less than or equal to 50%.

Thus, the correct answer is option A i.e., less than or equal to 50%.

Note: Recombination frequency is quantitatively measuring the linkage between the two genes during the meiosis. Also, Drosophila has 66 units of X-chromosomes and has less than 50% recombination frequency.