The Xlinked gene white in Drosophila melanogaster has more t

The X-linked gene white in Drosophila melanogaster, has more than 400 known alleles. We will concern ourselves with only four. The mutant allele white (w) we have talked about in class. It causes white eyes in homozygous females and hemizygous males. Another mutation, white-apricot (w^a) is dominant to w, and produces a pale yellow eye color called apricot. The last mutant is white-coffee (w^cf). When h omozygous, it causes a light brown color and is dominant to w. The w^a and w^cf alleles are codominant, and w^cf w^a flies have an eye color called dark apricot. The wild type allele, w^a, is dominant to all of the others, and produces the normal red eye color. Predict the phenotypic ratios (include sex) that would result from the following crosses. We will use X^a to indicate an X-chromosome with the wild-type allele, X^a to represent white-apricot, x^cf to represent white-coffee, and x^w for white. Y, of course, is the Y chromosome. X^cfX^w times X^aY Phenotypic ratio _______ A white eyed female and an apricot-eyed male Phenotypic ratio _______ The female progeny of cross b crossed with with coffee-eyed male. Phenotypic ratio _______ The male progeny of cross b crossed with with dark apricot females Phenotypic ratio _______

Solution

The x –linked gene white in drosophila melanogaster has more than 400 known alleles

The mutant white(w) we taked about in class .it causes white eyes in homozygous females

=

QUESTION B

ANSWER

A white eyed female and an apricot-eyes male

apricot eyes (w\"),-----allele--X^a

apricot-eyes male -------X^a Y

white eyed female----------- X^w X^w

X^w

X^w

X^a

X^w X^a

Dark apricot-eyes FEMALE

X^w X^a

White apricot-eyes FEMALE

Y

X^w Y

WHITE MALE

X^w Y

WHITE MALE

PHENOTYPIC RATIO =1:1

apricot-eyes FEMALE : WHITE MALE

QUESTION A

female----------- X^cf X^w

male -------X^a Y

X^cf

X^w

X^a

X^cf X^a

apricot-eyes FEMALE

X^w X^a

apricot-eyes FEMALE

Y

X^cf Y

WHITE MALE

X^w Y

WHITE MALE

PHENOTYPIC RATIO =1:1

	Xw	Xw
Xa	Xw Xa Dark apricot-eyes FEMALE	Xw Xa White apricot-eyes FEMALE
Y	Xw Y WHITE MALE	Xw Y WHITE MALE