For each gene, one DNA strand functions as a template for transcription to produce mRNA.
The base-pairing rules for DNA synthesis also guide transcription,
but uracil (
U) takes the place of thymine (
T) in RNA.
In translation, the
is read in the
5' - 3' direction as a sequence of base triplets, or
Each codon specifies an amino acid to be added to the growing polypeptide chain.