Question

1. The Pinzgauer breed of cattle has a distinctive white strip down the back, the result of a dominant gene for markings. Solid colored breeds, such as Angus, are homozygous recessive at this locus. Predict the outcome of the following mating:

1. The phenotypes of F from a Pinzgauer by Angus cross

2. The phenotype ratios for :

        F₁ by Angus cross

         F₁ by Pinzgauer cross

           F₁ inter se mated

Answer 1

let the alleles be A- dominant which results in white strip and a- recessive, results in solid color.

a) Pingauzer * Angus

AA * aa

Aa ( F1)

the phenotype of the F1 from a Pingauzer * Angus is cattle with a white strip on the back.

b) F1 * Angus

Aa * AA

	A	a
A	AA (white strip)	Aa (white strip)
A	AA (white strip)	Aa (white strip)

so all the progenies have a white stripe on the back.

so the phenotypic ratio is

cattle with white stripes: cattle with solid back =1:0

F1 * Pingauer

Aa * aa

	A	a
a	Aa (white strip)	aa (solid back)
a	Aa (white strip)	aa(solid back)

phenotypic ratio is

cattle with white stripes: cattle with solid back =1:1

F1* F1

Aa * Aa

	A	a
A	AA (cattle with white stripes)	Aa (cattle with white stripes)
a	Aa (cattle with white stripes)	aa ( cattle with solid back)

cattle with white stripe: cattlewih solid back=3:1