Drosophila has four pairs of chromosomes: the sex chromosomes (XX in the females; XY in the males) and three pairs of autosomes. You are studying a new mutant strain with blue eyes. You wish to know if blue eye colour is a dominant mutation and on which chromosome the blue eye locus can be found. When you cross a pure-breeding female blue-eyed fly with vestigial wings and spineless bristles to a male fly with wild type eye colour, wings, and bristles, all of the F1 progeny are completely wild type. An F1 male is backcrossed to a triple mutant female, producing the following progeny (remember that there is no crossing over in Drosophila males):
Wild type eyes, wings, and bristles:
72 females, 69 males
Wild type eyes and bristles, vestigial:
83 females, 77 males
Wild type wings, blue eyes, spineless:
60 females, 65 males
Blue eyes, spineless, vestigial:
62 females, 58 males
a. Is the mutation dominant or recessive? Explain.
b. Since you know that the locus for vestigial wings is on chromosome 2 and the locus for spineless bristles is on chromosome 3, what chromosome carries the locus for blue eyes? Show your work, including the step-by-step reasoning you used to arrive at your answer.
c. When an F1 female is backcrossed to a triple mutant male, the following 1,000 progeny are produced:
Wild type eyes, wings, and bristles:
90 females, 89 males
Wild type eyes and bristles, vestigial:
83 females, 98 males
Wild type eyes and wings, spineless:
37 females, 35 males
Wild type wings and bristles, blue eyes:
36 females, 34 males
Wild type wings, blue eyes, spineless:
92 females, 88 males
Wild type eyes, spineless, vestigial:
34 females, 39 males
Wild type bristles, vestigial, blue eyes:
33 females, 37 males
Blue eyes, spineless, vestigial:
90 females, 85 males
Calculate the map distance between blue eye and any linked genes. Show your work.
Drosophila has four pairs of chromosomes: the sex chromosomes (XX in the females; XY in the males) and three pairs of autosomes. You are studying a new mutant strain with blue eyes. You wish to know if blue eye colour is a dominant mutation and on which chromosome the blue eye locus can be found. When you cross a pure-breeding female blue-eyed fly with vestigial wings and spineless bristles to a male fly with wild type eye colour, wings, and bristles, all of the F1 progeny are completely wild type. An F1 male is backcrossed to a triple mutant female, producing the following progeny (remember that there is no crossing over in Drosophila males):
| Wild type eyes, wings, and bristles: | 72 females, 69 males |
| Wild type eyes and bristles, vestigial: | 83 females, 77 males |
| Wild type wings, blue eyes, spineless: | 60 females, 65 males |
| Blue eyes, spineless, vestigial: | 62 females, 58 males |
a. Is the mutation dominant or recessive? Explain.
b. Since you know that the locus for vestigial wings is on chromosome 2 and the locus for spineless bristles is on chromosome 3, what chromosome carries the locus for blue eyes? Show your work, including the step-by-step reasoning you used to arrive at your answer.
c. When an F1 female is backcrossed to a triple mutant male, the following 1,000 progeny are produced:
| Wild type eyes, wings, and bristles: | 90 females, 89 males |
| Wild type eyes and bristles, vestigial: | 83 females, 98 males |
| Wild type eyes and wings, spineless: | 37 females, 35 males |
| Wild type wings and bristles, blue eyes: | 36 females, 34 males |
| Wild type wings, blue eyes, spineless: | 92 females, 88 males |
| Wild type eyes, spineless, vestigial: | 34 females, 39 males |
| Wild type bristles, vestigial, blue eyes: | 33 females, 37 males |
| Blue eyes, spineless, vestigial: | 90 females, 85 males |
Calculate the map distance between blue eye and any linked genes. Show your work.
