A Mutant Gene That Produces Brown Eyes (Bw) Is Located $$\text { (brown-eyed mothers } \times \text { scarlet-eyed fathers) }$$

question 44

Essay

A mutant gene that produces brown eyes (bw) is located on chromosome #2 of Drosophila melanogaster, whereas a mutant gene producing bright red eyes, scarlet (st), is located on chromosome #3. Phenotypically, wild-type flies (with dull red eyes), whose mothers had brown eyes and whose fathers had scarlet eyes, were mated. The 800 offspring possessed the following phenotypes: wild type (dull red), white, scarlet (bright red), and brown. Most of the 800 offspring had wild-type eyes, whereas those with white eyes were the least frequent.
a) Using standard symbolism, diagram the cross from the P generation $$\text { (brown-eyed mothers } \times \text { scarlet-eyed fathers) }$$ and the F₁ generation. Be certain to provide the alleles of the mutant genes.
b) From the information presented above, how many white-eyed flies would you expect in the F₂ generation?

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