. Four comb shapes namely rose, pea, walnut and single in poultry are
known to be governed by two gene loci. The genotype R–P–produces
walnut comb, characteristic of the Malay breed : R–pp produces rose
comb, characteristic of the Wayandotte breed; rr P–produces pea comb,
characteristic of the Brahma breed ; rr pp produces single comb,
characteristic of the Leghorn breed.
a. If pure Wyandottes are crossed with pure Brahmas what phenotypic
ratios are expected in the F1 and F2 ?
c. A Malay hen was crossed with a Leghorn **** and produced a dozen
eggs, 3 of which grew into rose combed birds and 9 with walnut
combs. What is the probable genotype of hen ?
d. Determine the proportion of comb types that would be expected in
offspring from each of the following crosses:
1) Rrpp×RrPP,
2) rrPp×RrPp,
3) rrPP× RRPp,
4) RrPp×rrpp,
5) RrPp×RRpp,
6) RRpp × rrpp;
7) RRPP × rrpp ;
8) Rrpp × Rrpp;
9) rrPp × Rrpp;
10) rrPp × rrpp.
