What does it mean if an organism is homozygous for a trait?

An organism is described as homozygous for a trait when it possesses two identical alleles for that specific trait. This means that both copies of the gene, inherited from each parent, are the same, which can result in a uniform expression of that trait. For example, if the trait in question is flower color, an organism with two alleles for red flowers (RR) would display red flowers consistently, whereas an organism with one red allele and one white allele (Rr) would be heterozygous and might show a mixture of traits depending on the dominance of the alleles.

The concept of homozygosity is essential in genetics as it often leads to predictable outcomes in the phenotype (observable traits), especially in traits that are governed by a simple dominance-recessiveness relationship. Thus, understanding the importance of being homozygous aids in predicting inheritance patterns and trait expressions in breeding or genetic studies.