Question

In cattle, the polled (hornless) condition (H) is dominant over horned (h) phenotype. A particular polled bull is bred to three cows. Cow A, which is horned, produces a horned calf; a polled cow B produces a horned calf; and horned cow C produces a polled calf. What are the genotypes of the bull and the three cows, and what phenotypic ratios do you expect in the offspring of these three matings

Answer 1

Answer:

A)  

Hh *  hh

Hh, Hh, hh, hh

Out of four two calves are horned. Thus ratio of horned calves is $\frac{1}{2}$

B)

Hh * Hh

HH, Hh, Hh, hh

Out of four one calf is horned. Thus ratio of horned calf is $\frac{1}{4}$

C)

Hh * hh

Hh, Hh,hh, hh

Out of four two  are polled . Thus ratio of polled calves is $\frac{1}{2}$

Explanation:

Allele for dominant polled /hornless cattle is H

Allele for recessive horned cattle is h

A) Polled bull X horned Cow A ----> horned calf

This signifies that the polled bull is heterozygous with genotype Hh

Hh *  hh

Hh, Hh, hh, hh

Out of four two calves are horned. Thus ratio of horned calves is $\frac{1}{2}$

B) Polled bull X polled Cow B ----> horned calf

Both Bull ad cow are heterozygous with genotype Hh

Hh * Hh

HH, Hh, Hh, hh

Out of four one calf is horned. Thus ratio of horned calf is $\frac{1}{4}$

C) Polled bull X horned Cow C  ----> polled calf

Hh * hh

Hh, Hh,hh, hh

Out of four two  are polled . Thus ratio of polled calves is $\frac{1}{2}$