What does the term homozygous mean in genetic terms?

The term homozygous in genetic terms refers to an organism having two identical alleles for a particular trait. This means that the alleles inherited from each parent are the same, whether they are dominant or recessive. When an individual is homozygous for a trait, it influences how that trait is expressed in the phenotype. For example, if a plant has two identical alleles for flower color, either two dominant alleles (e.g., purple) or two recessive alleles (e.g., white), it will produce flowers that reflect that specific genetic makeup.

In contrast, having two different alleles for a trait is called heterozygous, which can result in the dominant allele being expressed if one is present. Carrying no alleles for a trait would imply that the gene is not present at all, which does not fit the definition of homozygous. Finally, expressing a recessive phenotype is not directly synonymous with being homozygous; an organism can be homozygous recessive and exhibit this phenotype, but it can also be heterozygous and express the dominant phenotype. Thus, the definition of homozygous is best captured by having two identical alleles for a trait.