Drosophila melanogaster has one pair of sex chromosomes (XX or XY) and three autosomes (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 F1 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, and no other
Phenotype | Female | Male |
wild | 63 | 59 |
pink* | 58 | 65 |
black, short | 55 | 51 |
black, pink, short | 69 | 60 |
*Pink indicates that the other two traits are wild type (normal). Similarly, black, short offspring are wild type for eye color.
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- 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_forwardRed eyes (r), brown color (b), and curled wings (c) are 3 recessive mutations that occur in house flies. These genes have already been mapped: r-b = 12 mu b-c = 18 mu r-c = 30 mu A fly with red eyes, brown color, and curled wings is crossed with a fly homozygous for the wild-type traits. The F1 males are crossed with females with the three mutant traits and 2000 progeny are produced. Find the number of observed double crossovers if the interference is 0.38. O 43 O 62 O 27 O 16arrow_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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