The alternative versions of a single gene are known as _________.

The alternative versions of a single gene are known as alleles. Alleles are different forms or variants of a gene that occupy the same position, or locus, on a chromosome. Each individual inherits two copies of each gene, one from each parent, and these copies can be the same allele or different alleles.

Alleles can vary in their DNA sequence, which can result in different traits or characteristics being expressed in individuals. For example, a gene for eye color may have different alleles, such as "brown" and "blue," which determine the specific eye color observed in individuals.