Question

A litter of pugs that Mrs. Stevens looked at had 5 puglets, 4 black and 1 fawn. When Mrs. Stevens was introduced to the proud pug parents, they were both black.What are the genotypes of the parent pugs? (Assume the letter for the colour allele is g)

Answer 1

The genotypes of the black parent pugs are most likely heterozygous (Gg), as they produced both black and fawn offspring. This scenario demonstrates simple Mendelian inheritance, where black is dominant and fawn is the recessive phenotype.

Step-by-step explanation:

The question pertains to genetics, specifically the inheritance of coat color in pugs, which is likely controlled by alleles similar to those in Labradors. In the case of the pug litter, since both parents are black but have produced a fawn puppy, this suggests that the black coat color is dominant over the fawn color. The presence of a fawn puglet indicates that each parent must have carried a hidden allele for the fawn color.

Given that 'g' represents the color allele and assuming that the black color is dominant (G) and the fawn color is recessive (g), the genotypes of the parent pugs would be Gg for both. This is because they both exhibit the black phenotype but have passed on the recessive fawn allele to their offspring. When using a Punnett square to predict the offspring genotypes, the litter would have a 75% chance (3 out of 4) of being black and a 25% chance (1 out of 4) of being fawn, which corresponds to the observed litter.

Answer 2

Given that both parents are black, that means that black is the dominant allele (G) and fawn is recessive (g).

This means that the parents may be GG or Gg.

If one of the parents is GG and the other is Gg, the genotypes of the offspring would be either GG or Gg, so all the litter would be black.

But if both parents are Gg, then the genotypes can be GG, Gg, or gg, making possible a fawn puglet.

So both parents are Gg.