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In chickens, comp shape is determined by alleles at two loci (R, r and P, p)....

In chickens, comp shape is determined by alleles at two loci (R, r and P, p). A walnut comb is produced when at least one dominant allele R is present at one locus, at least one dominant P allele is present at the second locus (i.e. 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 (rrpp), a single comb is produced. Progeny with what types of combs and in what proportions will result from the following crosses?

a. RR PP x rr pp

b. Rr Pp x rr pp

c. Rr Pp x Rr Pp

d. Rr pp x Rr pp

e. Rr pp x rr Pp

f. Rr pp x rr pp

please show step by step

Solutions

Expert Solution

Genotype of walnut comb = RRPP or RrPP or RRPp or RrPp

Genotype of rose comb =RRpp or Rrpp

Genotype of pea comb = rrPP or rrPp

Genotype of single comb = rrpp

a) RRPP * rrpp

Parent cross : RRPP (walnut comb) * rrpp (single comb)

Gametes walnut comb parent: RP

Gametes single comb parent : rp

Offspring : RrPp (walnut comb)

All offspring will have genotype RrPp. All offspring will have walnut combs

Probability of offspring with Walnut comb = 100%

b) RrPp * rrpp

Parent cross : RrPp (walnut comb) * rrpp (single comb)

Gametes of walnut comb parent : RP, Rp, rP, rp

Gametes of single comb parent : rp

Offspring : RrPp (walnut comb), Rrpp (rose comb), rrPp (pea comb), rrpp (single comb)

Offspring phenotypic artio : 1 (walnut comb) : 1(rose comb) :1(pea comb) : 1(single comb)

Probability of offspring with walnut comb = 1/4 = 25%

Probability of offspring with rose comb = 1/4 = 25%

Probability of offspring with pea comb = 1/4 = 25%

Probability of offspring with single comb = 1/4 = 25%

c) RrPp * RrPp

Parent cross : RrPp (walnut comb) * RrPp (walnut comb)

Gametes of walnut comb parent1: RP, Rp, rP, rp

Gametes of walnut comb parent2 :RP, Rp, rP, rp

Offspring :

RRPP (walnut comb), RRPp (walnut comb), RrPP (walnut comb),RrPp (walnut comb),

RRPp (walnut comb),RRpp (rose comb), RrPp (walnut comb), Rrpp(rose comb),

RrPP (Walnut comb), RrPp (walnut comb), rrPP (pea comb),rrPp (pea comb),

RrPp(walnut comb), Rrpp (rose comb), rrPp (pea comb), rrpp (single comb)

Offspring phenotypic ratio : 9 (walnut comb):3(rose comb):3 (pea comb):1(single comb)

Probability of offspring with walnut comb = 9/16

Probability of offspring with rose comb = 3/16

Probability of offspring with pea comb = 3/16

Probability of offspring with single comb = 1/16

d ) Rrpp * Rrpp

Parent cross : Rrpp (rose comb) * Rrpp (rose comb)

Gametes of rose comb parent 1 : Rp, rp

Gametes of rose comb parent 1 : Rp, rp

Offspring : RRpp (rose comb), Rrpp (rose comb), Rrpp (rose comb), rrpp (single comb)

Offspring phenotypic ratio :3(rose comb) :1(single comb)

Probability of offspring with rose comb = 3/4 = 75%

Probability of offspring with single comb = 1/4 = 25%

e) Rrpp * rrPp

Parent cross : Rrpp (rose comb) * rrPp (pea comb)

Gametes of rose comb parent : Rp,rp

Gametes of pea comb parent :rP, rp

Offspring : RrPp (walnut comb), Rrpp (rose comb), rrPp (pea comb), rrpp (single comb)

Offspring phenotypic ratio : 1(walnut comb) :1(rose comb) :1(pea comb) :1(single comb)

Probability of offspring with Walnut comb = 1/4 = 25%

Probability of offspring with Rose comb = 1/4 = 25%

Probability of offspring with Pea comb = 1/4 = 25%

Probability of offspring with Single comb = 1/4 = 25%

f) Rrpp * rrpp

Parent cross : Rrpp (rose comb) * rrpp (single comb)

Gametes of rose comb parent : Rp, rp

Gametes of single comb parent : rp

offspring : Rrpp (rose comb), rrpp (single comb)

Offspring phenotypic ratio : 1(rose comb):1(single comb)

Probability of offspring with rose comb = 1/2 = 50%

Probability of offspring with single comb = 1/2 = 50%

gladiator answered 2 months ago
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