Identifying gene mutations

The wild-type (normal) fruit fly, Drosophilia melanogaster, has straight wings and long bristles. Mutant strains have been isolated that have either curled wings or short bristles. The genes representing these two mutant traits are located on separate chromosomes. Carefully examine the data from the following five crosses shown below and answer the following questions.

 

Progeny

Cross

Straight wings, long bristles

Straight wings, short bristles

Curled wings, long bristles

Curled wings, short bristles

Straight, short x straight, short

30

90

10

30

Straight, long x straight long

120

0

40

0

Curled, long x straight, short

40

10

40

40

Straight, short x straight, short

40

120

0

0

Curled, short x straight, short

20

60

20

60

a.     Identify each mutation (curled wings and short bristles) as either dominant or recessive. In each case, indicate which crosses support your answer.

b.     Assign gene symbols and, for each cross, determine the genotypes of the parents. Remember that a superscript + is used to symbolize the wildtype mutation in Drosophilia.

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