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 (12th Edition)
- Dr. Disney has been raising exotic fruit flies for decades. Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb. He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw. He is able to establish flies that are homozygous for both mutant traits.He mates these two strains with each other. Dr. Disney then takes phenotypically wild- type females from this cross and mates them with double recessive males. In the resulting testcross progeny, he observes 500 flies that are of the following makeup:41 with baby blue eyes and pink wings207 with baby blue eyes only210 with pink wings only42 with wild-type phenotype14. Assuming the wild-type alleles for these two genes are b+ and pw+, what is the correct testcross of the F1 flies?A) b+ pw+/b pw ⋅ b pw/b pwB) b+ pw+/b pw ⋅ b pw+/b+ pwC) b+ pw/b pw+ ⋅ b pw/b pwD) b+ pw/b pw+ ⋅ b+ pw+/b pwE) b+ pw+/b pw ⋅ b+ pw/b…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 as diagrammed here. 1. Draw the meiotic prophase I chromosomes with maximal pairing from the inversion heterozygous female. 2. (continued) When a crossover occurs between v and f, please draw the resulting chromosomes in four gametes.arrow_forwardIn Drosophila, the wildtype eye color is black. In the laboratory, you screened for mutants than when homozygous results to different eye phenotypes. You found two mutants 1) red eye (re) and 2) white eye (we). You performed a complementation test and the resulting eye phenotype was gray. From the results, what conclusion can you make? A. There was complementation, thus the two mutations are alleles of different genes. B. There was no complementation, thus the two mutations are alleles of different genes. C. The two mutations failed to complement, thus they are alleles of different genes. D. The two mutations failed to complement, thus they are alleles of the same genes. E. The two mutations complemented, hence they are likely controlled by different genes.arrow_forward
- A man suffered from rare a skin condition that included thickening of the skin and the formation of loose spines that were periodically sloughed off. He was called by the locals as “porcupine man”. He married and had six sons, all of whom had the same condition. He also had three daughters, all of whom were unaffected. What might you theorize about the location of the abnormal gene? In maize, a dominant allele A is necessary for seed color, as opposed to colorless (a). Another gene has a recessive allele wx that results in waxy starch, as opposed to normal starch (Wx). The two genes segregate independently. An Aa WxWx plant is test crossed. What are the phenotypes and relative frequencies of offspring? (show the workflow to reach your answers) all sub-questions carries equal grades): Consider three gene pairs Aa, Bb, and Cc, each of which affects a different character. In each case, the uppercase letter signifies the dominant allele and the lowercase letter the recessive allele.…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, a cross was made between females and wild-type males. The female parents expressed the three X-linked recessive traits miniature wing (m), ebony body (e) and cinnabar eye (c). In the F1, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F2 generation, and 1500 offspring were produced. 412 403 211 Miniature wing, ebony body, cinnabar eye Wild type Ebony body, cinnabar eye Miniature wing Miniature wing, cinnabar eye Ebony body Miniature wing, ebony body Cinnabar eye 224 103 96 23 28 (i) Using proper nomenclature, determine the genotypes of the females and males in generation P and F1. (ii) What is the correct order of the genes? (iii) Construct a genetic map showing the correct order and distances between these genes.arrow_forward
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