0. In Drosophila, the gene for cinnabar eye color is onchromosome 2, and the gene for scarlet eye color is onchromosome 3. A fly homozygous for both recessivecinnabar and scarlet alleles (cn/cn; st/st) is white-eyed.a. If male flies (containing chromosomes with thenormal gene order) heterozygous for cn and st allelesare crossed to white-eyed females homozygous forthe cn and st alleles, what are the expected phenotypes and their frequencies in the progeny?b. One unusual male heterozygous for cn and st alleles,when crossed to a white-eyed female, produced onlywild-type and white-eyed progeny. Explain the likelychromosomal constitution of this male.c. When the wild-type F1 females from the cross withthe unusual male were backcrossed to normal cn/cn;st/st males, the following results were obtained:wild type 45%cinnabar 5%scarlet 5%white 45%Diagram a genetic event at metaphase I that couldproduce the rare cinnabar or scarlet flies among theprogeny of the wild-type F1 females.
0. In Drosophila, the gene for cinnabar eye color is on
chromosome 2, and the gene for scarlet eye color is on
chromosome 3. A fly homozygous for both recessive
cinnabar and scarlet alleles (cn/cn; st/st) is white-eyed.
a. If male flies (containing chromosomes with the
normal gene order) heterozygous for cn and st alleles
are crossed to white-eyed females homozygous for
the cn and st alleles, what are the expected
b. One unusual male heterozygous for cn and st alleles,
when crossed to a white-eyed female, produced only
wild-type and white-eyed progeny. Explain the likely
chromosomal constitution of this male.
c. When the wild-type F1 females from the cross with
the unusual male were backcrossed to normal cn/cn;
st/st males, the following results were obtained:
wild type 45%
cinnabar 5%
scarlet 5%
white 45%
Diagram a genetic event at metaphase I that could
produce the rare cinnabar or scarlet flies among the
progeny of the wild-type F1 females.
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