What describes different versions of a single gene?

The correct answer, which describes different versions of a single gene, is alleles. Alleles are variations of a gene that arise due to differences in the DNA sequence at that particular locus. For example, a gene that determines flower color in a plant might have a purple allele and a white allele. These alleles can lead to different traits being expressed, such as the flower color.

Mutations refer to changes in the DNA sequence but do not specifically define variations of a gene in the same way that alleles do. Genotypes indicate the genetic makeup of an organism for a specific trait, detailing which alleles are present but not representing the variations themselves. Phenotypes, on the other hand, are the observable characteristics or traits of an organism resulting from the interaction of its genotype with the environment. While phenotypes can be influenced by alleles, they are not the versions of the gene itself.