. In 1919, Calvin Bridges began studying an X-linkedrecessive mutation causing eosin-colored eyes inDrosophila. Within an otherwise true-breedingculture of eosin-eyed flies, he noticed rare variantsthat had much lighter cream-colored eyes. By intercrossing these variants, he was able to make a truebreeding cream-eyed stock. Bridges now crossedmales from this cream-eyed stock with true-breedingwild-type females. All the F1 progeny had red (wildtype) eyes. When F1 flies were intercrossed, the F2progeny were 104 females with red eyes, 52 maleswith red eyes, 44 males with eosin eyes, and14 males with cream eyes. Assume that thesenumbers represent an 8:4:3:1 ratio.a. Formulate a hypothesis to explain the F1 and F2results, assigning phenotypes to all possiblegenotypes.b. What do you predict in the F1 and F2 generations if the parental cross is between truebreeding eosin-eyed males and true-breedingcream-eyed females?c. What do you predict in the F1 and F2 generationsif the parental cross is between true-breedingeosin-eyed females and true-breeding creameyed males?
. In 1919, Calvin Bridges began studying an X-linked
recessive mutation causing eosin-colored eyes in
Drosophila. Within an otherwise true-breeding
culture of eosin-eyed flies, he noticed rare variants
that had much lighter cream-colored eyes. By intercrossing these variants, he was able to make a truebreeding cream-eyed stock. Bridges now crossed
males from this cream-eyed stock with true-breeding
wild-type females. All the F1 progeny had red (wildtype) eyes. When F1 flies were intercrossed, the F2
progeny were 104 females with red eyes, 52 males
with red eyes, 44 males with eosin eyes, and
14 males with cream eyes. Assume that these
numbers represent an 8:4:3:1 ratio.
a. Formulate a hypothesis to explain the F1 and F2
results, assigning
genotypes.
b. What do you predict in the F1 and F2 generations if the parental cross is between truebreeding eosin-eyed males and true-breeding
cream-eyed females?
c. What do you predict in the F1 and F2 generations
if the parental cross is between true-breeding
eosin-eyed females and true-breeding creameyed males?
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