Question

Background Information: In incomplete dominance, the heterozygous genotype will express a phenotype somewhere in-between the dominant and the recessive. With codominance, the heterozygous genotype will express both phenotypes. Answer in

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In a chestnut horse, their coat (hair) color can be reddish brown (AA), light red/pink (Aa), and creamy white (aa). Fill in the Punnett square and determine the expected genotypes and phenotypes from crossing heterozygous and heterozygous parents.

Answer 1

When crossing two heterozygous chestnut horses, there are three possible genotypes for the offspring due to incomplete dominance: AA (reddish brown), Aa (light red/pink), and aa (creamy white), with an expected genotypic and phenotypic ratio of 1:2:1.

Step-by-step explanation:

Incomplete Dominance in Horses

In the case of incomplete dominance in horse coat color, when two heterozygous (Aa) chestnut horses are crossed, the resulting offspring can have three possible genotypes with associated phenotypes: AA (reddish brown coat), Aa (light red/pink coat), and aa (creamy white coat). Completing a Punnett square for this cross would involve placing one parent's alleles on the top and the other parent's alleles on the side to predict the possible genotypic outcomes.

The Punnett square would look like this:

Top row (Parent 1): A a

• Side column (Parent 2): A a

This results in the following genotypic combinations in the offspring:

1 AA (reddish brown coat)

• 2 Aa (light red/pink coat)
• 1 aa (creamy white coat)

The expected genotypic ratio is 1:2:1, which also translates to the same phenotypic ratio because of the incomplete dominance mode of inheritance in chestnut horses.

Therefore, the genotypes and associated phenotypes of the offspring from such a cross are expected to be:

Reddish brown: homozygous dominant AA

1. Light red/pink: heterozygous Aa
2. Creamy white: homozygous recessive aa