Question

5) You are given the task of creating a genetic map of three genes of Drosophila melanogaster. The genes are all located on the same chromosome. The genes are for the body color, eye color, and antenna formation. The alleles for body color are yellow and gray (wild-type), the alleles for eye color are sepia and red (wild-type) and the alleles for the antenna are short and normal (wild-type). The mutant alleles for body and eye color are recessive, while the mutant allele for antenna formation is dominant. You follow the procedure for determining the order and map distance for the genes and obtain the following data:

Short, gray, sepia = 240

Short, yellow, red = 2

Short, yellow, sepia = 500

Short, gray, red = 22

Normal, yellow, red = 270

Normal, gray, sepia = 5

Normal, yellow, sepia = 15

Normal, gray, red = 444

Hints for drawings: size matters! Don’t draw all genes equidistant. If two genes are further away from each other than another set, make sure to draw it that way.

Based on the data given:

a) Define each gene and allele. Based on how you defined the alleles, what was the genotype and phenotype of the P gen? Make sure to notate alleles properly and to draw the chromosomes correctly. Make sure the genes are in the correct order.

b) What was the genotype and phenotype of the F1 gen? Make sure to notate alleles properly and to draw the chromosomes correctly. Make sure the genes are in the correct order.

c) What was the genotype and phenotype of the Test cross that was performed? Make sure to notate alleles properly and to draw the chromosomes correctly. Make sure the genes are in the correct order.

d) What are all of the map distances between the genes given? Make sure to draw the chromosomes correctly, the genes are in the proper order, and units are used.

Answer 1

Map distance between N and S is 2.94 mapunits whereas map distance between S and Y is 34.5 mapunits.

The explanation is given below: