In the domestic fowl, a number of genes influence the shape of the comb. The eff
ID: 52564 • Letter: I
Question
In the domestic fowl, a number of genes influence the shape
of the comb. The effects of the R/r and P/p alleles is shown in
the table below. Note that stands for either the dominant or
recessive allele, e.g. P represents both PP and Pp.
Allele Associated Comb Shape
R_ pp rose comb
rrP_ pea comb
R_P_ walnut comb
rrpp single comb
Determine the ratio of phenotypes of the progeny arising from
crosses between the following parents. Give your answer as a ra-
tio reduced to the lowest number in the order walnut comb:rose
comb:pea comb:single comb. So, if the ratio is 2 walnut comb to
2 single comb, enter 1:0:0:1.
RR Pp x rr Pp
Explanation / Answer
Parents RR Pp X rrPp
Gamets RP Rp & rP rp
walnut comb:rosec comb:pea comb:single comb
3 : 1 : 0 : 0
rP rp RP RrPP walnut comb RrPp walnut comb Rp RrPp walnut comb Rrpp rose comb