In cows, long hair is dominant to short hair. If a cow is heterozygous for long hair, what percentage of cells undergoing meiosis will carry the dominant allele?

In cows, if long hair is represented by a dominant allele (let's denote it as "L") and short hair by a recessive allele (denote it as "l"), a heterozygous cow for long hair would have the genotype "Ll."

During meiosis, the parent cell undergoes a process of gamete formation that involves the separation of homologous chromosomes. In the case of a heterozygous individual, each gamete will receive one allele from each pair of alleles. Specifically, half of the gametes will receive the dominant allele (L) and the other half will receive the recessive allele (l). Therefore, when these gametes are produced, 50% will carry the dominant allele for long hair, while the other 50% will carry the allele for short hair.

Thus, in terms of cells undergoing meiosis, 50% of these cells will carry the dominant allele for long hair, which makes this the correct interpretation of the question.