In chickens, comb shape is determined by alleles at two loci. A walnut comb is p
ID: 3473513 • Letter: I
Question
In chickens, comb shape is determined by alleles at two loci. A walnut comb is produced when at least one dominant allele A is present at one locus and at least one dominant allele B is present at the second locus. A rose comb is produced when at least one dominant allele is present at the “A-locus” and two recessive alleles are present at the “B-locus”. A pea comb is produced when two recessive alleles are present at the “A-locus” and at least one dominant allele is present at the “B-locus”. When the genotype is a double homozygous recessive, a single comb is produced.
Give the phenotypic ratios that will results from the following crosses: AaBb x aaBb
Explanation / Answer
From the cross between AaBb and aaBb-
AaBb x aaBb
Gametes
aB
ab
AB
AaBB walnut
AaBb walnut
Ab
AaBb walnut
Aabb rose
aB
aaBB pea
aaBb pea
ab
aaBb pea
aabb single
There are three walnuts comb, three pea, and one- one rose and single progenies.
Therefore the phenotypic ratio (rose:walnut:pea:single) is 1:3:3:1.
Gametes
aB
ab
AB
AaBB walnut
AaBb walnut
Ab
AaBb walnut
Aabb rose
aB
aaBB pea
aaBb pea
ab
aaBb pea
aabb single
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.