Three genes on the Drosophila X chromosome exami following recombination rates: (1) yellow-white, 0.5% (2) white-miniature, Which two genes are physically closest together? are examined pairwise. It is determined that they have the

A) Yellow and white
B) White and miniature
C) Yellow and miniature
D) All three are about equally spaced
E) One cannot tell from this information 34-3

The correct answer is option A, that is, yellow and white.

Explanation:

A phenomenon in which chromosomes of a homologous pair interchange equal sections with each other is termed as crossing over. One mu or map unit signifies 1 percent recombination phenotypes. One can witness less recombination when two genes are situated very close to one another, and in contrast, there will be more recombination when the two genes are situated very far from each other.  

In the given case, as it is mentioned that the rate of recombination between white and yellow is 0.5 percent, thus, it signifies that the genes of yellow and white are physically present very close to each other.