With reference to the eye color phenotypes produced by the recessive, autosomal, unlinked...

With reference to the eye color phenotypes produced by the recessive, autosomal, unlinked brown and scarlet loci in Drosophila (see Figure), predict the F1 and F2 results of the following P1 crosses. (Recall that when both the brown and scarlet alleles are homozygous, no pigment is produced, and the eyes are white.)

(a) wild type × white

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(b) wild type × scarlet

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(c) brown × white

FIGURE

Figure 4–10 A theoretical explanation of the biochemical basis of the four eye color phenotypes produced in a cross between Drosophila with brown eyes and scarlet eyes. In the presence of at least one wild-type bw+ allele, an enzyme is produced that converts substance b to c, and the pigment drosopterin is synthesized. In the presence of at least one wild-type st+ allele, substance e is converted to f, and the pigment xanthommatin is synthesized. The homozygous presence of the recessive st or bw mutant allele blocks the synthesis of the respective pigment molecule. Either one, both, or neither of these pathways can be blocked, depending on the genotype.