In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced. Give genotypes for comb shape of the parents in the following cross: Rose crossed with pea produces 20 walnut offspring.

a. RR PP * rr pp

b. RR Pp * rr pp

c. Rr PP * rr pp

d. Rr Pp * rr pp

e. Rr pp * rr pp

Question

Carissa Parks

Biology

28 August, 04:41

In chickens, comb shape is determined by genes at two loci (R, r and P, p). A walnut comb is produced when at least one dominant gene R is present at one locus and at least one dominant gene P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant gene is present at the first locus and two recessive genes are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive genes are present at the first locus and at least one dominant gene is present at the second (genotype rr P_). If two recessive genes are present at the first and the second locus (rr pp), a single comb is produced. Give genotypes for comb shape of the parents in the following cross: Rose crossed with pea produces 20 walnut offspring.

a. RR PP * rr pp

b. RR Pp * rr pp

c. Rr PP * rr pp

d. Rr Pp * rr pp

e. Rr pp * rr pp

+4

Answers (1)

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Cornelius Daniels · Answer 1

in the obtained options, there is no dominant gene for the crossed pairs, therefore, no answer would be correct, however, when assigning a dominant character to the P gene, the correct answer would be:

E. Rr pp * rrPp

Explanation:

According to the information obtained we deduce:

Comb shape is produced by R and P

Comb of walnuts with an R or a P

Pink comb: 1 dominant P and R at the first locus and 2 recessive at the next locus

Pea comb: 2 recessive at the start and one dominant in the next position

1 single comb: 2 recessive at both loci

Rr pp * rr Pp will produce from the interbreeding: 2 walnuts, 1 single and 1 pea offspring.

We deduce that for the pink comb the genotype is: Rrpp

and for the pea comb it is rrPp

Rr pp * rr Pp generates crosslinks containing RrPp, rrPp, rrpp as children in a 2: 1: 1 ratio.