Comb shape in chickens results from the epistatic interaction of two genes. The first gene (T/t)...

Comb shape in chickens results from the epistatic interaction of two genes. The first gene (T/t) affects the basic shape of the comb such that: TT and Tt results in a walnut (normal) comb while tt results in pea comb. The recessive allele (r) of a second gene (R/r) modifies the first gene, but the dominant allele (R) does not. Thus RR and Rr has no effect on comb shape, while rr paired TT or Tt produces a rose comb and rr paired with tt produces a single comb

a. Report the phenotype for each of the genotypes below:

TTRr = _________________________________

TtRR = _________________________________

ttRr = __________________________________

Ttrr = __________________________________

b. A farmer makes the following genetic cross among his chickens: Male = Ttrr x Female = ttRr

What are the phenotypes of the parent chickens?

Report all possible genotypes and phenotypes of offspring.

Solutions

Expert Solution

TTRr =Walnut comb (since RR and Rr has no effect on comb shape)

TtRr = Walnut comb (since RR and Rr has no effect on comb shape)

ttRr = Pea comb ( Since RR and Rr has no effect on comb shape)

Ttrr = Rose comb (since rr affects the comb shape and masks walnut comb)

Genotype of male parent: Ttrr

phenotype of male parent: Rose comb

genotype of female parent: ttRr

phenotype of female parent: Pea comb

Parent cross: Ttrr (male) * ttRr (female)

gametes of male parent: Tr, tr

gametes of female parent: tR, tr

offspring: TtRr (walnut comb), Ttrr (rose comb) ,ttRr (pea comb), ttrr (single comb)

genotypic ratio: 1 (TtRr) :1 (Ttrr) :1(ttRr) :1 (ttrr)

Phenotypic ratio - 1 (walnut comb) : 1 (rose comb) : 1 (pea comb) : 1 (single comb)

gladiator answered 1 year ago

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