Homozygous individuals are characterized by what genetic condition?

• A. Having two different alleles
• B. Having a pair of identical alleles
• C. Having three copies of a gene
• D. Having no alleles at a locus

Answer: (B)

Homozygous individuals are characterized by having a pair of identical alleles at a specific locus on homologous chromosomes. This means that both alleles inherited from each parent for a particular gene are the same. For example, if an individual has two alleles that are both for the dominant trait (AA) or both for the recessive trait (aa), they are considered homozygous for that gene.

Understanding homozygosity is important because it can influence the expression of traits. In a homozygous individual, since both alleles are identical, they will consistently express the same phenotype. In contrast, heterozygous individuals, who have two different alleles at a locus, may express a phenotype that reflects a mix of both alleles or may display the dominant trait if one exists.

The other options describe different genetic situations, like heterozygosity (two different alleles), polyploidy (three or more copies of a gene), or a complete lack of allele expression at a locus, which does not correspond to the definition of homozygosity.