Genes are loci of DNA that contain the instructions for hereditary traits. Most traits are influenced by multiple genes and gene-environment interactions. Genes can acquire mutations over time, leading to different alleles that encode variant proteins and cause phenotypic changes. The concept of a gene continues to evolve as new discoveries are made about regulatory regions, exons, and non-coding functional RNA. Broadly, any discrete locus of heritable genomic sequence that affects traits through expression or regulation can be defined as a gene.