Part 1: The balancer chromosome CyO carries a dominant mutation, Cy , which caus

Question

Part 1: The balancer chromosome CyO carries a dominant mutation, Cy, which causes curly wings. CyO is balancer for the second chromosome. The balancer chromosome TM3 carries a dominant mutation, Sb, stubble, which causes the bristles to be short. TM3 is a balancer for the third chromosome.   You obtain two Drosophila stocks.

The first has the genotype, CyO / lethal-2, while the second has the genotype TM3 / lethal-3. If you cross these two stocks together, what frequency of each of the following phenotypes do you expect to see in the progeny?

_____ straight wings and long bristles (wild-type)

_____ curly wings and long bristles

_____ straight wings and short bristles

_____ curly wings and short bristles

Part 2: Consider one of the flies with curly wings and short bristles.   What is its likely genotype?

Part 3: You cross one fly of this type (one with curly wings and short bristles, the F1 progeny of the two stocks described in part 1) with a wild-type fly. What frequency do you expect of each of the following genotypes now?

_____ straight wings and long bristles (wild-type)

_____ curly wings and long bristles

_____ straight wings and short bristles

_____ curly wings and short bristles

Explanation / Answer

Part1:

1----straight wings and long bristles (wild-type)

3---curly wings and long bristles

3---straight wings and short bristles

9---curly wings and short bristles

Part 2: The genotype will be Cy/Tm

Part 3:

1---straight wings and long bristles (wild-type)

1--- curly wings and long bristles

1-- straight wings and short bristles

1---curly wings and short bristles

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