What does it mean for an animal to be homozygous for a particular gene?

When an animal is described as homozygous for a particular gene, it means that it possesses two identical copies of that gene. This can occur for either version of the gene, known as alleles, whether those alleles are dominant or recessive. For example, if a gene exists with alleles A and a, a homozygous animal might have either two copies of the dominant allele (AA) or two copies of the recessive allele (aa).

Being homozygous can significantly influence the traits that the animal expresses. If the alleles are for a dominant trait, the trait will be expressed; if they are for a recessive trait, the recessive trait will be expressed. This genetic uniformity can be crucial for breeding programs and research in agricultural biotechnology, where trait predictability is highly valued.

The other options do not accurately describe homozygosity. Having different alleles indicates a heterozygous condition, showing recessive traits only applies specifically to situations where the organism is homozygous recessive, and the description of being genetically modified refers to intentional alterations made through biotechnology, rather than a natural genetic configuration.