Passage the Fruit Fly Drosophila Melanogaster Is Frequently Used as a a Model

Passage
The fruit fly Drosophila melanogaster is frequently used as a model system to investigate neurological disorders.  The genes Abl, Enabled (Ena) , and receptor protein tyrosine phosphatase (PTP) are involved in axonal guidance during neuronal development and are all believed to operate in the same pathway.  To investigate interactions between PTP and either Ena or Abl, fly lines were developed in which mutations of each gene were easily identifiable by eye characteristics.  In flies that would normally have white eyes, a dominant mutation that inactivates PTP results in red and white eyes; a dominant Ena mutation yields orange eyes (or red and orange if the PTP and Ena mutations are both present) ; and a dominant Abl mutation yields elongated eyes.  Using these fly lines, the following experiments were conducted.Experiment 1Females heterozygous for PTP (eePp) were crossed with males heterozygous for Ena (Eepp) .  F1 generation males and females, each with red and orange eyes, were then selected and crossed with each other to produce an F2 generation.  Flies with two mutant Ena alleles (EE) , as well as those with two mutant PTP alleles and at least one mutant Ena allele (EePP) , did not survive past the larval stage.Experiment 2PTP and Abl are located on the same chromosome.  Females with the PTP mutation on one copy of the chromosome and the Abl mutation on the other copy were crossed with wild-type males.  In Drosophila, recombination occurs only in female gametes.  Progeny with parental and recombinant genotypes are shown in Table 1.  F1 males with red and white elongated eyes were then crossed with homozygous PTP mutant females.  This produced an F2 generation in which 50% of both male and female progeny had elongated eyes.Table 1  Phenotypes of 500 F1 Flies
Like humans, male flies have a single X chromosome, whereas females have two X chromosomes.  Unlike humans, female Drosophila can store sperm and fertilize multiple eggs over the course of several days after a single mating.  Researchers ensured that females were virgins prior to setting up each cross to avoid contamination.
Adapted from Song JK, Giniger E, Desai CJ. The receptor protein tyrosine phosphatase PTP69D antagonizes Abl tyrosine kinase to guide axons in Drosophila. Mech Dev. 2008;125(3-4) :247-56.
-A female virgin heterozygous for both PTP and Ena (EePp) mated with a single, unknown male that was produced by the parental cross described in Experiment 1.  If 25% of the resulting progeny died in the larval stage, the genotype of the male was most likely:

A) Eepp
B) eePP
C) eepp
D) EePP

Correct Answer:

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