How is a homozygous organism defined?

A homozygous organism is defined as one that has identical alleles at corresponding loci on homologous chromosomes. This means that for a specific gene, the two alleles (one from each parent) are the same, whether they are both dominant or both recessive. For example, if an organism has two alleles for a gene that code for the same trait, such as both being for blue eyes (represented as “bb” for the recessive trait), that organism is considered homozygous.

This definition is crucial in genetics because homozygosity can significantly affect the organism's phenotype (observable traits) and can influence breeding patterns, genetic variation, and the inheritance of traits. Understanding this concept helps in predicting how traits will be passed on to the next generation and is fundamental in fields such as horticulture, animal breeding, and conservation genetics.

The other choices touch on different genetic concepts: differing traits suggest heterozygosity, alternative forms of a trait refer to alleles themselves, and lack of identifiable traits doesn’t pertain to any genetic classification. Each of these options represents distinct genetics principles and traits that do not define a homozygous organism.