Question

In Holstein cattle the spotting of the coat is due to a recessive gene, while a solid-colored coat is dominant. Two heterozygous solid animals are crossed. What would be the expected genotypes and phenotypes of the offspring?

Answer 1

Answer:

In Holstein cattle when two heterozygous animals are crossed for the characteristic coat color, the offspring will be individuals with solid coat and spotted coat in a 3:1 ratio.

Explanation:

Since in Holstein cattle the solid color coat is dominant (S), and the spotted coat is recessive (s), each heterozygous individual has the genotype Ss.

The result of crossing two individuals of Holstein cattle heterozygous can be seen in Punnet's Square:

Ss X Ss

Alleles  S     s

S          SS   Ss

s           Ss   ss

Genotypes

• Ss 50%
• SS 25%
• ss 25%

Ratio of genotypes SS:Ss:ss is 3:1:1

Phenotypes

• Individuals with solid color coat 75% (50% Ss and 25% SS).
• Individuals with a spotted coat 25%.

Ratio solid color:spotted color 3:1