Question

The normal cloven-footed condition in swine is produced by the recessive allele m, while the mule-footed condition is produced by the dominant allele M. White coat color is governed by the dominant allele of another locus B, and black by its recessive allele b. A black mule-footed sow (female pig) is mated with a white cloven-footed boar (male pig). All of their 36 offspring are white, but 17 have mule feet and 19 have cloven feet. What are the probable genotypes of the parents?

A. MmBb and mmBb, respectively
B. Mmbb and mmBB, respectively
C. Mmbb and mmBb, respectively
D. MMbb and mmBB, respectively

Answer 1

The probable genotypes of the black mule-footed sow and white cloven-footed boar are Mmbb and mmBB, respectively, based on the phenotypes of their offspring.

Step-by-step explanation:

The question is asking about the genotypes of two pigs that were crossed, based on the phenotypic outcomes of their offspring. Since all 36 offspring are white, we can determine that white coat color is dominant and the black mule-footed sow must carry at least one dominant allele for white coat color. Given that the mule-footed condition is dominant (M) and the sow is mule-footed, her genotype at the foot locus must have at least one M allele. Since the boar is cloven-footed and all offspring are white, the boar's genotype must be homozygous recessive for foot condition (mm) and have at least one dominant allele for white coat color (B).

Considering that no offspring is black, both parents must provide a B allele, so neither parent can have two b alleles. Since some offspring have cloven feet, the sow must not be homozygous MM, otherwise all offspring would have mule feet. The most likely genotypes of the parents are therefore Mmbb for the black mule-footed sow and mmBB for the white cloven-footed boar, making the correct answer B. Mmbb and mmBB, respectively.