What do we call each inherited copy of a gene?

Each inherited copy of a gene is referred to as an allele. Alleles are different versions of the same gene that are located at the same position, or locus, on homologous chromosomes. For example, a gene that determines flower color might have one allele for red flowers and another for white flowers. The combination of alleles inherited from each parent contributes to the organism's genotype, which in turn influences its phenotype, or physical expression of traits.

Understanding alleles is crucial in genetics, as they define the variation in traits and contribute to the diversity seen within a species. In contrast, the other terms—chromatid, genotype, and phenotype—relate to broader concepts in genetics but do not specifically identify the individual copies of a gene. A chromatid refers to one half of a duplicated chromosome, genotype refers to the genetic makeup of an organism, and phenotype describes the observable characteristics or traits resulting from the interaction of the genotype with the environment.