The following are the recombination frequencies for a set of genes found on the same chromosome: X-W 7% W-Y 10% X-Z 13% W-Z 20% X-Y 17% What is the correct order for these genes using a linkage map analysis? Between which two genes is crossing over most likely to occur?

Options have not been provided for the question. They are as follows:

What is the correct order for these genes using a linkage map analysis?

A. Z-X-Y-W

B. X-W-Z-Y

C. W-X-Y-Z

D. Y-W-Z-X

E. Z-X-W-Y

F. Y-X-W-Z

Between which two genes is crossing over most likely to occur?

A. B and D

B. X and Z

C. X and W

D. X and Y

E. W and Z

F. Y and W

G. Y and Z

Answer:

Correct order for these genes using a linkage map analysis: E. Z-X-W-Y

Two genes between which the crossover is most likely to occur: G. Y and Z

Explanation:

According to linkage concept, recombination frequency between two genes = distance between two genes in cM

Here, smallest distance is between X and W (7cM) so they are present next to each other. Distance between X and Y is 17cM and between W and Y is 10cM so W is present between X and Y. Distance between X and Z is 13 cM. Since on one side of X, W and Y are already present Z lies on the other side. So, the final gene order comes out to be, Z-X-W-Y.

According to the gene order, Y and Z genes are farthest from each other. Chances of crossover or recombination increases with increasing distance between genes. So, Y and Z have the highest probability to show crossing over.