In terms of genetics, what does the term 'allele' refer to?

The term 'allele' refers specifically to a variant form of a gene. Genes, located on chromosomes, come in different versions, which are known as alleles. For instance, a gene controlling flower color in a plant may have one allele for red and another for white. These variations can influence an organism's traits depending on their dominance, interaction, and genetic background, contributing to the phenotypic expression observed.

This distinction is essential because it highlights how genetic diversity arises within a population, leading to different traits and characteristics. Understanding alleles helps in studying inheritance patterns and the underlying genetic mechanisms that govern various biological processes. The other options describe different genetic concepts, such as proteins involved in gene expression, observable traits that result from gene activity, or the total genomic content of an organism, but they do not define what an allele is.