Triplet genetic code.
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 mRNA is read in the 5' - 3' direction as a
sequence of base triplets, or codons.
Each codon specifies an amino acid to be added to the growing