Advanced Placement (AP) Biology Practice Exam

In genetics, what does the term "homozygous" refer to?

1. Different alleles at a gene locus

2. Identical alleles at a gene locus

3. Segregated alleles

4. Diverse genetic traits

The correct answer is: Identical alleles at a gene locus

The term "homozygous" refers to having identical alleles at a specific gene locus. This means that an individual carries two copies of the same allele, which can be either dominant or recessive. For example, if a plant has two alleles for flower color that are both for red flowers, it is considered homozygous for that trait. In the context of genetics, this is important because homozygous individuals can express traits more uniformly, making it easier to predict the outcomes of breeding or inheritance patterns. By contrast, having different alleles at a gene locus would be referred to as "heterozygous," which can lead to more variability in traits exhibited. Understanding these terms is crucial for studying inheritance patterns and genetic diversity.