Genes "Switch On"
When a gene "switches on," it eventually makes a protein, but it does not do so directly. First the gene codes an intermediary molecule called mRNA. To transfer a gene's information from DNA to mRNA, base pairing is used. However, there is one change: an adenine base (A) in the DNA matches with a new base called uracil (U) in the mRNA. This difference helps to distinguish mRNA from DNA.