What does it mean if an animal is homozygous for a particular gene?

When an animal is described as homozygous for a particular gene, it means that it has two copies of the same allele for that gene. Alleles are different versions of a gene that can exist at a specific locus on a chromosome. Therefore, when an organism possesses two identical alleles (either both dominant or both recessive) for a given gene, it is considered homozygous.

This genetic configuration can influence the expression of traits in the animal. For example, if both alleles are dominant, the dominant trait will be expressed. Conversely, if both alleles are recessive, the recessive trait will be expressed. This is essential in breeding and genetics as homozygosity can affect traits and predictability of offspring characteristics.

The other options reflect different genetic scenarios: having one copy of each allele indicates a heterozygous condition, while having two different alleles or having no alleles does not align with the definition of homozygosity. Understanding these distinctions is fundamental to genetics, particularly in agricultural biotechnology where such knowledge assists in breeding programs and genetic research.