In sheep, the allele for white wool (A) is dominant over the allele for black wool (a). How would you determine the genotype of a white ram, or male sheep?

To determine the genotype of a white ram, you can perform a test cross. Here's how you can do it:

1. Obtain a ram with white wool and unknown genotype (let's call it ram X) and another ram with black wool (let's call it ram Y). Ram Y should be homozygous for the black wool allele (aa).
2. Mate ram X with ram Y. Allow them to breed naturally or assist in the breeding process.
3. Observe the offspring produced from this cross.

From the resulting offspring, you can determine the genotype of the white ram, X, based on their phenotypes. If all the offspring have white wool, then the white ram must be homozygous dominant (AA). This is because if a white ram is heterozygous (Aa), it would produce both white and black offspring when mated with a black ram (aa).

However, if some of the offspring have black wool, then the white ram must be heterozygous (Aa) since the black wool allele is recessive. In this case, approximately half of the offspring should have white wool, and the other half should have black wool.

By performing this test cross and observing the phenotypes of the offspring, you can determine the genotype of the white ram.