A normal Drosophila (fruit fly) has both brown and scarlet pigment granules in its eyes, which appear red as a result. Brown (bw) is a recessive allele on chromosome 2 that, when homozygous, results in brown eyes due to the absence of scarlet pigment granules. Scarlet (st) is a recessive allele on chromosome 3 that, when homozygous, results in scarlet eyes due to the absence of brown pigment granules. Any fly homozygous for recessive alleles at both genes produces no eye pigment and has white eyes.

The following results were obtained from crosses:

P brown-eyed fly!scarlet-eyed fly

F1 red eyes (both brown and scarlet pigment present)

F2 9/16 red : 3/16 scarlet : 3/16 brown : 1/16 white

a. Assign genotypes to the P and F1 generations.

b. Design a testcross to verify the F1 genotype, and predict the results