White eyes can also result by crossing brown-eyed females (bw) with scarlet eyed

Question

White eyes can also result by crossing brown-eyed females (bw) with scarlet eyed males (st) (that is, when both mutant alleles are present).A cross is made between white-eyed females with the genotype w//w (otherwise, homozygous for wild type alleles) and white-eyed males hemizygous for the wild type allele (w+ ).

In the following problem, the F1 from the previous problem has a cross.

the genotypes from the parents are

Xw+ Xw, bw bw+, st st+ x Xw Y, bw bw+, st st+

This is the way it was solved.

My question is, why is the second category scarlet 3/32 that color?

unde rmy logic, it wont be scarlet as in this category st is recessive.

What would be the criteria to determine the phenotype of each genotype?

If there is two wild tipes ex. Xw+ Xw bw+ as genotype, what would be the genotype?

Thank you.

bw bw t c) Expected F2 phenotypic ratios. Show your work. p 2 w St st + bwt 3/4 3/32 scar le 2 3/32 brow n /3 2 white v2 st+3 bw bw V1 bwt 314 2. 3/52 white /32 wh CONCEPT PROBLEM 4 How can the same phenotvpe stem from many different genotypes? Explain. some gene are estatlct wnich mea thet the maj k

Explanation / Answer

In drosophila , if there is mutation in brown pigment ( bw), then red color cannot be produced resulting in brown color eyes . If there is mutation in scarlet gene (st) , then the color of the eyes will be bright red and called as scarleteyes. If there is mutation in both brown and scarlet eyes (w+), then the eyes will be white . So, here ( st,st ) codes for scarlet pigment . if its (st+, st) , (bw,bw) then it will code for brown . if (bw, w+), it will code for white. That is why ( st,st ) codes for scarlet pigment. Here w+ for white because , white is dominant over other eyes.

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