In genetics, what is the term for different forms of a gene?

The correct term for different forms of a gene is "alleles." Alleles arise due to variations in the DNA sequence of a gene, and each individual can inherit different alleles from their parents. For example, a gene that determines flower color in a plant may have one allele for red flowers and another for white flowers. Individuals can be homozygous for a trait if they have two identical alleles, or heterozygous if they have two different alleles.

In contrast, chromosomes refer to the structures that organize and contain genetic material, while genomes refer to the complete set of genes or genetic material present in an organism. Phenotypes are the observable traits or characteristics of an organism, which are influenced by both genetic makeup (genotype, which includes alleles) and environmental factors. Thus, "alleles" specifically addresses the variation in gene forms, making it the correct answer in this context.