Drosophila melanogaster has one pair of sex chromosomes (XX or XY) and three pairs of autosomes, referred to as chromosomes II, III, and IV. A genetics student discovered a male fly with very short (sh) legs. Using this male, the student was able to establish a pure breeding stock of this mutant and found that it was recessive. She then incorporated the mutant into a stock containing the recessive gene black (b, body color located on chromosome II) and the recessive gene pink (p, eye color located on chromosome III). A female from the homozygous black, pink, short stock was then mated to a wild-type male. The F, males of this cross were all wild type and were then backcrossed to the homozygous b, p, sh females. The F2 results appeared as shown in the following table. No other
*Other trait or traits are wild type.
- (a) Based on these results, the student was able to assign short to a linkage group (a chromosome). Which one was it? Include your step-by-step reasoning.
- (b) The student repeated the experiment, making the reciprocal cross, F1 females backcrossed to homozygous b, p, sh males. She observed that 85 percent of the offspring fell into the given classes, but that 15 percent of the offspring were equally divided among b + p, b + +, +shp, and + sh + phenotypic males and females. How can these results be explained, and what information can be derived from the data?
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Concepts of Genetics (11th Edition)
- One of the X chromosomes in a particular Drosophila female had a normal order of genes but carried recessive alleles of the genes for yellow body color (y), vermilion eye color (v), and forked bristles (f), as well as the dominant X-linked Bar eye mutation (B). Her other X chromosome carried the wild-type alleles of all four genes, but the region including y+, v+, and f+ (but not B+) was inverted with respect to the normal order of genes. This female was crossed to a wild- type male in the cross diagrammed her. The cross produced the following male offspring:* table in figure a. Why are there no male offspring with the allele combinations y v f+, v+ v+ f, y v+ f+, or y+ v f (regardless of the allele of the Bar eye gene)?b. What kinds of crossovers produced the y v f b+ and v+ y+ f+ B offspring? Can you determine any genetic distances from these classed of progeny?c. What kinds of crossovers produced the y+ v f+ B+ and y v+ f B offspring?arrow_forwardOne of the X chromosomes in a particular Drosophila female had a normal order of genes but carried recessive alleles of the genes for yellow body color (y), vermilion eye color (v), and forked bristles (f), as well as the dominant X-linked Bar eye mutation (B). Her other X chromosome carried the wild-type alleles of all four genes, but the region including y+, v+, and f+ (but not B+) was inverted with respect to the normal order of genes. This female was crossed to a wild-type male in the cross diagrammed her. The cross produced the following male offspring: Y v f B 48 y+ v+ f+ B+ 45 y v f B+ 11 y+ v+ f+ B 8 y v f B 1 y+ v+ f+ B+ 1 a. Why are there no male offspring with the allele combinations y v f+, v+ v+ f, y v+ f+, or y+ v f (regardless of the allele of the Bar eye gene)? b.What kinds of crossovers produced the y v f b+ and v+ y+ f+ B offspring? Can you determine any genetic distances from these classed of progeny? c. What kinds of crossovers produced the…arrow_forwardTwo different strains of Drosophila, strain A and strain B, each has a recessive mutation that results in abnormally bright red eye color. (Wild type flies have brownish red eye color). When a homozygous strain A fly is crossed with a homozygous B fly, all of the progeny have the dominant wild type eye color. The wild type-eyed progeny were allowed to breed among themselves to produce the F2 generation. The F2 generation consisted of 92 wild type and 74 bright red-eyed flies. Write the genotype(s) of the flies in each generation. Use a low dash (e.g. A_ B_) to indicate genotypes that could be either homozygous or heterozygous) a) parental strain A b) parental strain B c) wild type progeny (F1) d) wild type F2 e) bright-eyed F2arrow_forward
- Drosophila females heterozygous for three recessive mutations, a, b, and c , were crossed to males homozygous for all three mutations.The cross yielded the following results: in the image Q. Construct a linkage map showing the correct order of these genes and estimate the distances between them.arrow_forwardConsider the following variations in Drosophila melanogaster, relative to the wild-type: White eyes are a recessive trait—the gene of which is found in Chromosome I (X). Vestigial wings are a recessive trait—the gene of which is found in Chromosome II. Aristapedia is a dominant trait—the gene of which is found in Chromosome III. Being homozygous for this condition is lethal. Cross the following mutant females with a wild-type (homozygous) male. Show the Punnett square and obtain the genotypic and phenotypic ratios of the first filial generation (F1). Female with white eyes Q4: Show the Punnett squares and obtain the genotypic and phenotypic ratios of the first filial generation (F1) and second filial generation (F2) of the following crosses. Note: The F2 generation can be obtained by crossing one male and one female from the F1 generation. Female with white eyes and vestigial wings and wild-type malearrow_forwardIt is assumed that in Drosophila the following genotypes produce phenotypes. َA- B- = Red color A- bb = Plum color aa B- = Magenta color aa bb = White color The third latent genotype, cc, kills homozygous Plums, but has no effect on other genotypes. Also, genotype C- does not produce a large phenotype. If first-generation Drosophilas are heterozygous for all of these genes and interbreed, what phenotypic ratios are expected in society?arrow_forward
- You are working in the lab with strains of Drosophila that have either normal legs or abnormally short legs and you are studying the gene responsible. You know that normal legs are dominant to short legs. You come across a misplaced fly with normal legs, but you are not sure of his genetic background and you want to keep him in your experiments. (Without doing a molecular analysis), How could you figure out whether he was heterozygous or homozygous for the leg gene that you are studying? (Describe what you would do and how the results would answer the question.) What is the procedure you described above called?arrow_forwardThe coloration of calico cats is also the result of the inactivation of one of a female cat's sex chromosomes. In females, two X chromosomes are present in all cells but only one is active, the inactive one is called a BARR BODY. This is why the coat color is random, even among cloned calico cats that have identical genomes. Calico is a coat color found in cats, which is caused by a SEX-LINKED, CODOMINANT allele.arrow_forward. In Drosophila melanogaster many eye color mutations are known. One such recessive mutation is called brown (bw) and gives brown eyes instead of the wild type dark red eyes. Another recessive mutation is scarlet (st) which gives bright red eyes. The bw st double mutant has white eyes. A brown-eyed male was crossed to a scarlet- eyed female. The F1 progeny were wildtype. When the F1 males were test-crossed to bw/bw st/st females the following progeny phenotypes were produced: 1/4 wildtype, 1/4 brown, 1/4 scarlet, 1/4 white. These results show that the two genes are? Select all that apply a)linked and 25cM apart b)sex linked c)linked d)assorting independently Please answer asap and in short and content should not be palgarised please answerarrow_forward
- In Drosophila melanogaster, black body (b) is recessive to gray body (b+), purple eyes (pr) are recessive to red eyes (pr+), and vestigial wings (vg) are recessive to normal wings (vg+). The loci coding for these traits are linked with the following map distances: b--------8cM--------pr------------------30cM-----------------vg The interference among these genes is 0.2. A fly with black body, purple eyes, and vestigial wings is crossed with a fly homozygous for gray body, red eyes and normal wings. The female progeny were then crossed with males that have black body, purple eyes, and vestigial wings. a) Illustrate the Parental and F1 cross b) If 2000 progeny are produced from this test cross, what will be the phenotypes that will result and how many of each will there be?arrow_forwardAn undergraduate researcher in your lab is studying mutations affecting the wings of Drosophila melanogaster. She has identified two mutant phenotypes of interest: bent wings (be), which are recessive to the wild-type straight wings (be+), and apterous (ap) mutants (which are wingless). The apallele is recessive to the wild-type allele (ap+), which allows wings to develop. If a homozygous bent-winged fly (which possesses the normal allele of apterous) is crossed with a homozygous wingless fly (which possesses the normal allele of bent wings), what phenotypic ratio would you expect to observe in the F2 generation of this cross? a) Please indicate the ratio, including the genotypes and phenotypes of all phenotypic classes. Phenotype: Genotype(s) corresponding to this phenotype Phenotypic ratio: (Be sure to NAME the classes in the ratio). B) Please NAME and DEFINE the type of gene interaction illustrated in this example.arrow_forwardIn Drosophila, the sepia mutation (se, chromosome 3, position 26) results in dark brown eyes, while cinnabar (cn, chromosome 2, position 57.5) results in bright orange-red eyes. True breeding, wild type females are mated with true breeding males homozygous recessive for both traits. Fill in the chart with phenotypic ratios that would be expected in the F2 generation. Use the space provided to show your work.arrow_forward
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