What is an alternative form of a gene at a particular locus called?

An alternative form of a gene at a particular locus is known as an allele. Each gene can have multiple variations, and these variations can influence traits in an organism. For instance, the gene that determines flower color in a plant could have different alleles resulting in red, white, or blue flowers. The presence of different alleles can lead to genetic diversity and can impact how traits are expressed in an individual.

Traits refer to the observable characteristics or features of an organism, which are determined by the interaction of alleles but are not the variations themselves. Genotype describes the specific alleles an individual possesses for a particular gene, while phenotype is the expression of those genotypes, encompassing the observable traits. Thus, the correct identification of an "alternative form of a gene" clearly points to the term allele.