What is a homozygous organism?

A homozygous organism is defined as one that carries two identical alleles for a specific trait. This means that for the gene in question, both alleles inherited from the parents are the same, whether they are dominant or recessive. For example, if the trait in question is flower color, a homozygous organism could have two alleles for red flowers (RR) or two alleles for white flowers (rr). This genetic uniformity can influence the organism's appearance and behavior when it comes to the traits governed by those alleles.

In contrast, an organism with two different alleles for a trait is termed heterozygous, which introduces variation in traits. The third option refers to an organism with multiple alleles, which applies to traits influenced by more than two allelic forms but does not define homozygosity specifically. Lastly, the notion of an organism with no alleles does not accurately portray any biological organism since all individuals possess alleles inherited from their parents. Thus, the description of a homozygous organism as one with two identical alleles for a trait is precise and reflects a fundamental concept in genetics.