Question

The wild-type eye color in the fruit fly Drosophila melanogaster is dark red, as a result of a mixture of bright red and brown pigments. Enzyme A is encoded by the a gene and is required to synthesize the bright red pigment. A lack of red pigment results in a somewhat brown eye color. You cross two fruit flies who are heterozygous for a recessive mutation that completely inactivates the a gene. What proportion of their offspring will have a recessive eye color phenotype? a. All of the offspring b. 3/4 c. 1/2 d. 1/4 e. None of the offspring 7. "Dumpy" is a commonly used dominant mutant phenotype in the nematode worm C. elegans. Two dumpy individuals are crossed to each other, and this cross produces 210 dumpy and 68 wild-type individuals. If one of the dumpy individuals used in this cross was mated with a wild type, what dumpy:wild-type ratio would we observe in the offspring? a. 0:1 b. 1:0 c. 1:1 d. 1:3 e. 3:1 8. A recessive X-linked gene mutation is known to generate premature baldness in males but is without effect in women. If a heterozygous female marries an affected male, what proportion of all their children is expected to be prematurely bald? a. 1/4 b. 1/8 c. 1/16

          The wild-type eye color in the fruit fly Drosophila melanogaster is dark red, as a result of a
mixture of bright red and brown pigments. Enzyme A is encoded by the a gene and is required to
synthesize the bright red pigment. A lack of red pigment results in a somewhat brown eye color.
You cross two fruit flies who are heterozygous for a recessive mutation that completely
inactivates the a gene. What proportion of their offspring will have a recessive eye color
phenotype?
a. All of the offspring
b. 3/4
c. 1/2
d. 1/4
e. None of the offspring
7. "Dumpy" is a commonly used dominant mutant phenotype in the nematode worm C. elegans.
Two dumpy individuals are crossed to each other, and this cross produces 210 dumpy and 68
wild-type individuals. If one of the dumpy individuals used in this cross was mated with a wild
type, what dumpy:wild-type ratio would we observe in the offspring?
a. 0:1
b. 1:0
c. 1:1
d. 1:3
e. 3:1
8. A recessive X-linked gene mutation is known to generate premature baldness in males but is
without effect in women. If a heterozygous female marries an affected male, what proportion of
all their children is expected to be prematurely bald?
a. 1/4
b. 1/8
c. 1/16

Added by Daniel I.

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