Mendelian Genetic problems

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Mendelian Genetic problems

Post by Alla on Wed Aug 06, 2008 11:01 pm

AlwaysLearning wrote:Hi,

You seem helpful from your posts.

Please could you help with my question?

White leghorn chickens have normal pigment genes, but are white because of a dominant color inhibiting gene (I). White Plymouth rock chickens are white because they are homozygous for a recessive loss of pigmentation gene (c) that behaves much like the coat color gene (C/c) in mice. The genes are unlinked and neither is sex-linked. A true-breeding white leghorn (II CC) is crossed with a true-breeding white Plymouth Rock chicken (ii cc).
a. What is the genotype of the F1 progeny?
b. What is the phenotype of the F1 progeny?
c. Draw a branching diagram of the cross between 2 F1 chickens
d. What is the phenotypic ratio of the F2 progeny of the original cross?

Thank you, any help is appreciated.

First, you need to a cross of IICC x iicc (F0). Once you do that you do that you will see that all progeny (F1) will be the same heterozygous genotype IiCc which will be white (w) because of dominant I allele.

For the next part you will need to draw a diagram of IiCc x IiCc cross that will give you genotypes of the F2 progeny. Since the alleles are not linked the possible gametes for each parent are IC, Ic, iC, and ic. The genotypes would be: IICC (w), 2IICc (w), 2IiCC (w), 4IiCc (w), IIcc (w), 2Iicc (w), iiCC, 2iiCc, iicc (w). You will see that the ratio from this cross is 13 white to 3 colored.

Good luck!

Alla
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