One of the alternative forms of a gene that governs a trait such as hair color is called what?

• A. Locus
• B. Gene
• C. Allele
• D. Chromosome

Answer: (C)

Allele is one of the alternative forms a gene can take that influences a trait. Different alleles arise from variations in the gene’s DNA sequence and they occupy the same spot (the locus) on homologous chromosomes. These variants can lead to differences in the trait, such as hair color, especially when some alleles are dominant and others recessive. For example, a hair color gene might have a allele for dark hair and another for light hair; depending on which alleles a person inherits, the phenotype changes. The other terms describe something different: a locus is simply the location of a gene on a chromosome, a gene is the basic unit of heredity, and a chromosome is the structure that carries many genes. Alleles specifically refer to the different versions that govern a trait.