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.
-Of the genes tested in the passage, which are autosomal?EnaAblPTP

Question

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.
-Of the genes tested in the passage, which are autosomal?EnaAblPTP

Quizplus · Accepted Answer

11ecba2d_0ff3_99b0_a3bf_472a8cdb78b6_MD0008_00 In mammals and many insects, genetic traits are generally passed to the next generation in either an autosomal or a sex-linked manner. Of the chromosomes in a zygote, two are sex chromosomes (X,Y) and the remaining ones are called autosomes. Sex-linked traits arise due to the expression of alleles present on an organism's sex chromosomes. Because the X chromosome contains significantly more genes than the Y chromosome, the majority of sex-linked traits are linked to the X chromosome. Due to sex determination, male offspring (XY) receive their X chromosome from their mother (XX) and their Y chromosome from their father (XY). Because males have only one X chromosome and cannot compensate with another, males in a population generally express recessive X-linked traits in higher proportions than their female counterparts. Autosomal traits arise due to the expression of alleles present on an organism's autosomes. These alleles are passed to offspring through inheritance of the parental autosomes. Because males and females all have the same number of autosomes, autosomal traits are generally expressed in the same proportions in males as in females. The passage states that males in the first cross of Experiment 1 were heterozygous for Ena, suggesting that they had two different copies of the gene. Therefore, Ena cannot be on the X chromosome and must be autosomal (Number I). In Experiment 2, F2 males and females have the same ratios of normal-shaped eyes to elongated eyes. Based on the cross used to generate the F2 generation, if Abl were sex-linked, all females would have elongated eyes (dominant) and all males would have normal eyes (recessive). Because this is not the case, Abl must be autosomal (Number II). Because PTP is on the same chromosome as Abl, it must also be autosomal (Number III). Educational objective: Genetic traits may be autosomal or sex-linked (X chromosome). Because males have only one X chromosome, sex-linked recessive traits tend to be present at greater rates in males than in females, whereas autosomal traits are present in the same proportions in both.

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