Question

Scarlet (st) is recessive to wild type (st+) and sepia (se) is recessive to wild type (se+). Both genes are located on chromosome 3 in Drosophila melanogaster. If a true breeding female wild type fly mated with a true breeding male scarlet; sepia fly, the F1 generation flies would have the alleles of these two genes in the ___.

Answer 1

Answer:

cis configuration

Explanation:

Given both the male and female are true breeding which means that they are homozygous for the involved genes.

Female: wild type = st+st+se+se+

Male: scarlet, sepia = ststsese

During mating, female will produce all st+se+ gametes and male will produce all stse gametes. When the gametes fuse, the F1 progeny will have st+se+ alleles on same chromosome ( which was obtained from the female parent ) and stse alleles on another chromosome ( which was obtained from the male parent ). When dominant alleles of two genes are present on same chromosome and recessive alleles are present on other chromosome, alleles of these genes are present in cis configuration. Hence, these alleles are present in cis configuration. If dominant and recessive allele of the genes are present on the same chromosome, the alleles are in trans configuration.