Question

Drosophila, the genes for eye color, wing shape, and wing length are located on chromosome II. Purple eyes (pr), arc bent wings (a), and vestigial wings (vg) are the mutant forms of the wild type traits red eyes, straight wings, and long wings, respectively. You've discovered some data in your genetics laboratory which indicates that the distance between vg and pr is 12.5 m.u., the distance between a and pr is 44.7 m.u., and the distance between a and vg is 32.2 m.u.

Required:

From this information, deduce the order of these genes on chromosome II and identify which gene is in the middle.

Answer 1

The order of the genes on chromosome II is pr-vg-a, and the gene in the middle is a.

Step-by-step explanation:

The order of the genes on chromosome II can be determined by analyzing the distances between them. From the given data, we can deduce that the order of the genes is pr-vg-a which means that the gene for purple eyes (pr) is closest to the gene for vestigial wings (vg) and farthest from the gene for bent wings (a).

The gene that is in the middle is the one with the largest distance from both the other genes. In this case, the gene for bent wings (a) is in the middle as its distance from vg (32.2 m.u.) is greater than its distance from pr (44.7 m.u.).

Answer 2

This is the order of the genes on chromosome II and the gene in the middle:

Order of genes:

vg - a - pr

Gene in the middle:

a

How to find gene order?

To determine the order of the genes, use the following information:

The distance between vg and pr is 12.5 m.u.

The distance between a and pr is 44.7 m.u.

The distance between a and vg is 32.2 m.u.

From this information, the distance between vg and a is 32.2 m.u., which is the sum of the distances between vg and pr and a and pr. This means that the genes must be in the order vg - a - pr.

The gene in the middle is a because it is between vg and pr.

Therefore, the order of the genes on chromosome II is vg - a - pr, and the gene pr" (purple eyes) in the middle.