Which term describes an organism that contains two dominant or two recessive alleles?

The term that describes an organism with two identical alleles for a trait, whether they are both dominant or both recessive, is homozygous. When an organism is homozygous, it means that their genetic makeup for a specific gene consists of two copies of the same allele. For example, if an organism has two dominant alleles (AA) or two recessive alleles (aa) for a given trait, it is classified as homozygous for that trait.

Homozygosity is important in genetics because it can influence the expression of traits and the inheritance patterns within a population. The concept is essential for understanding how traits are passed from parents to offspring and can be observable in breeding experiments or studies of heredity.

The other terms, while relevant to genetics, hold different meanings. Heterozygous refers to having two different alleles for a trait, genotype pertains to the genetic constitution of an organism, and phenotype refers to the observable characteristics or traits that result from the genotype. Thus, the distinction between homozygous and heterozygous is crucial for understanding genetic variation in organisms.