Genetic variants in non-coding DNA can influence phenotype

When a cell copies a gene to make mRNA (the instructions to make a protein), this is called gene expression. Only around 1-2% of the genome is genes; the rest contains code that controls gene expression. A genetic variant in a non-gene (so called "non-coding") section of the genome can affect gene expression. Non-coding DNA affects gene expression because it is where RNA polymerase starts copying the gene for protein synthesis. Genetic variants in non-coding DNA can impact gene expression and therefore an organism’s phenotype.