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.
