Question

In Drosophila, the X-linked recessive mutation vermilion (XV) causes bright red eyes, in contrast to the brick-red eyes of wild type (X+). Part A separate autosomal recessive mutation (br), causes the eyes to be brown. Predict the F1 results of the following cross: normal females x white males. (Assume that the parents are homozygous.) Flies carrying both mutations lose all pigmentation and are white-eyed. Label the diagram by dragging the labels to the appropriate targets. Note: not all labels will be used. Reset Help 0 1/4 1/2 female, normal female, brown eyes female, vermilion eyes female, white eyes male, normal male, brown eyes male, vermilion eyes male, white eyes 3/4

Answer 1

For production of vermilion, wild type and brown eye colour, two genes are responsible. Brown eye colour gene interacts with vermilion gene.

Genotype X^vX^v BRBR produces vermilion red eye colour in female. In male X^v Y BRBR produces vermilion male

Genotype X⁺X⁺BRBR or X⁺X^vBRbr produces normal brick red eyed female and X⁺YBRBR or X⁺YBRbr produces normal male. That means for production of normal phenotype, at least one normal gene for both types necessary.

Genotype X⁺X⁺ brbr produces brown female and also brown male (X⁺Ybrbr).

Genotype X^vX^v brbr produces white eyed female and male (X^vYbrbr)

Cross: Normal female X white eyed male

X⁺X⁺BRBR x X^vYbrbr

Gametes X⁺BR and X^vbr and brY

	Xvbr	brY
X+BR	X+XvBRbr (Normal female)	X+YBRbr (Normal male)
X+BR	X+XvBRbr (Normal female)	X+YBRbr (Normal male)

So, result is 1 normal female : 1 normal male