Florida Biology EOC Practice Test

Which condition involves having identical alleles for a trait?

1. Codominance

2. Genotype

3. Heterozygous

4. Homozygous

The correct answer is: Homozygous

The correct response is rooted in the definition of genetic terminology. The condition described by having identical alleles for a trait is referred to as being homozygous. When an organism is homozygous for a specific gene, it possesses two copies of the same allele, whether they are dominant or recessive. For instance, an individual with two alleles for blue eyes (bb) or two alleles for brown eyes (BB) is homozygous for eye color. In contrast, codominance pertains to a situation where two different alleles are expressed simultaneously, leading to a phenotype that displays characteristics of both alleles in the organism. Genotype, on the other hand, is the term used to describe the genetic makeup of an organism, encompassing all alleles it possesses, regardless of whether they are identical or different. Lastly, heterozygous describes the condition in which an organism has two different alleles for a particular trait, such as having one allele for brown eyes and another for blue eyes (Bb). Therefore, the distinct definition of homozygous aligns perfectly with the question posed about identical alleles.