You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a brown (B/by) spider with a pure-breeding green spider. Predict the phenotype of the progeny.

Question

Booth

Biology

30 November, 20:17

You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), br (red), bg (green), and by (yellow). B is dominant to all the other alleles, and by is recessive to all the other alleles. The bg allele is dominant to by but recessive to br. You cross a brown (B/by) spider with a pure-breeding green spider. Predict the phenotype of the progeny.

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Maximus Weber · Answer 1

50% are brown. 50% are green.

Explanation:

Given;

B allele is for brown color, so B = brown,

br = red,

bg = green,

by = yellow.

B is dominant over all;

bg is dominant over by;

br is dominant over bg;

by is recessive to all other alleles.

Here, cross between brown (B/by) and pure green (bg/bg).

B/by * bg/bg

progeny

Genotype = B/bg, B/bg, by/bg and by/bg.

Phenotype = B/bg = brown;

by/bg = green

So, 1/2 are brown and 1/2 are green.