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

• A. Loci
• B. Phenotypes
• C. Alleles
• D. Genotypes

Answer: (C)

Alleles are the different forms a gene can take. Each gene sits at a specific location on a chromosome, and slight changes in its sequence create these alternative versions. In organisms with two copies of each chromosome, you usually have two alleles for each gene—one inherited from each parent. The combination of those two alleles is the genotype, while the trait you actually see, such as eye color or flower color, is the phenotype. So alleles are the variants that drive genetic diversity, while loci are where those genes sit, genotypes describe the two-allele makeup, and phenotypes describe the observable traits.