entyKD V 10. In chickens, comb shape is determined by alleles at two loci (R, r

Question

entyKD V 10. In chickens, comb shape is determined by alleles at two loci (R, r and P, p). A waln ut comb t least one dominant allele R is present at one locus and at least one is produced when dominant allele P is present at a second locus (genotype R_ P_). A rose comb is produced when at least one dominant allele is present at the first locus and tw present at the second locus (genotype R pp). A pea comb is produced when t alleles are present at the first loc o recessive alleles are wo recessi us and at least one dominant allele is present at the second (genotype IT P). If two recessive alleles are present at the first and at the second locus (rr pp), a single comb is produced. Progeny with what types of combs and in what pr will result from the following crosses? b. RrPp x rrpp c. RrPp x RrPp d. Rrpp x Rrpp c. Rrpp x ITPp f. Rrpp x rrpp I haing lacerate leaves was crossed with

Explanation / Answer

Hi,
The genotype and corresponding phenotypes are given in the question. We have to cross each combinations and determine the phenotypes.
a. RRPP x rrpp
Gametes: RP x rp
F1 = RrPp
This will be a Walnut comb. All of them will be Walnut.

b. RrPp x rrpp
Gametes: RP Rp rP rp x rp

F1: RrPp walnut
   Rrpp rose
   rrPp pea
   rrpp single
Ratio will be 1:1:1:1

c. RrPp x RrPp
This is a dihybrid cross. We know that the ratio of F1 in dihybrid cross = 9:3:3:1. Most dominant will be in ratio 9 and most recessive will be in ratio 1.
So here also we get, walnut: rose: pea: single :: 9:3:3:1
Walnut = RRPP, RrPP, RRPp, RrPp
Rose = RRpp, Rrpp
pea = rrPP, rrPp
single = rrpp

d. Rrpp x Rrpp
Gametes: Rp rp x Rp rp
F1: RRpp = Rose
Rrpp = Rose
rRpp = Rose
rrpp = single
Ratio = 3:1::Rose: single

e. Rrpp x rrPp
Gametes: Rp rp x rP rp
F1:    RrPp = walnut
   Rrpp = Rose
   rrPp = Pea
   rrpp = single
ratio = 1:1:1:1

f. Rrpp x rrpp
gametes: Rp rp x rp
F1 =    Rrpp = Rose
   rrpp = single
ratio= 1:1

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