Question

1. Genes D, E, F, and G are located on the same chromosome. The distances between the genes are below:

Relationship	Map Unit Distance
G - D	11
G - E	7
G - F	22
E - F	15
D - E	4

What is the order of the genes on the chromosome?

Answer 1

Answer- 4 genes D,E,F,G are located on the same chromosome and the distance between the genes are given in map unit distance, the correct order of the genes on the chromosome is G,E,D, F.

Explanation- To find the correct order of genes on the chromosome , we will make a gene map in which we arrange the genes in according to the distance and relationship among the genes for the data given in the question. Gene map is an arrangement of genes on the chromosome and with the help of which we can determine the correct order of genes on a chromosome.

• There is a simple way to draw a gene map of genes on a chromosome. We will assume the map unit distance equals to cm in order to draw the map in an easy way otherwise map unit distance is the unit to describe the distance between genes on the basis of linkage and recombinant frequency. 1 map unit distance is equals to 0.01 recombinant frequency.
• Firstly we take that two genes which have largest difference between them i.e. having largest map unit distance between them, then we adjust or put other genes in their between or at appropriate position according to the map unit distance between the genes.
• In the question, largely apart genes are G-F , 22 map unit distance, so we firstly take G-F and then put other two genes according to the distance among them. Gene map is drawn in the image attached,

Hence, the correct order of genes D,E,F,G, is G-E-D-F.