In chickens, comb shape is determined by two independent genes (R and P). A walnut comb is produced when at least one dominant allele R is present at one gene locus and at least one dominant allele P is present at a second gene locus (genotype R_ P_). A rose comb is produced when at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive alleles are present at the first locus and at least one dominant allele is present at the second (genotype rr P_). If two recessive alleles 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 2 walnut, 1 single, and 1 pea 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

Biology

Danielle Kline

22 July, 10:14

In chickens, comb shape is determined by two independent genes (R and P). A walnut comb is produced when at least one dominant allele R is present at one gene locus and at least one dominant allele P is present at a second gene locus (genotype R_ P_). A rose comb is produced when at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus (genotype R_ pp). A pea comb is produced when two recessive alleles are present at the first locus and at least one dominant allele is present at the second (genotype rr P_). If two recessive alleles 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 2 walnut, 1 single, and 1 pea 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

+2

Answers (2)

Know the Answer?

Izaiah Simmons · Answer 1

B) Rr pp * rr Pp

Explanation:

In the given question, the genotype of four shapes of comb have been provided which are:

1. Walnut comb - R_ P_

2. Rose comb - R_ pp

3. Pea comb - rr P_

4. single comb - rr pp

If a cross is made between the

Rose x pea

R_ pp x rr P_

The progenies are

single : walnut : pea

rr pp : R_ P_ : rr P_

In order to determine the missing allele of parent:

1. Recessive homozygous is taken into account

2. We known that one allele is contributed by male and one by female therefore in recessive homozygous rrpp,

3. In rr - one r is contributed by male and one by female therefore one 2 comes from rr P_ and therefore one allele will come from R_ pp.

4. In pp - one allele is contributed by the R_ pp and one allele by rr P_ therefore missin allele is p.

Thus, the genotype of the parents is - Rr pp * rr Pp.

Kallie Mack · Answer 2

Option B, Rr pp * rr Pp

Explanation:

Given

Walnut Comb is produces when one dominant allele R is present at one gene locus and at least one dominant allele P is present at a second gene locus - R * P*

Rose Comb - at least one dominant allele is present at the first locus and two recessive alleles are present at the second locus - R * pp

Pea comb - two recessive alleles are present at the first locus and at least one dominant allele is present at the second - rr P*

Single comb - two recessive alleles are present at the first and the second locus - rrpp

Parent are rose combed and pea combed

For being rose genotype must be R * pp

and for being pea combed genotype must be rr P*

Rr pp x rr Pp

will produce

Walnut comb with genotype Rr Pp

Single comb with genotype rrpp

and pea comb with genotype rrPp

Hence, option B is correct