The genetic code is degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three nonsense codons. In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase.

The genetic code refers to the DNA alphabet (A, T, C, G), the RNA alphabet (A, U, C, G), and the polypeptide alphabet (20 amino acids). The central dogma describes the flow of genetic information in the cell from genes to mRNA to proteins.

consensus — DNA sequence that is used by many species to perform the same or similar functions. codon — three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation. core enzyme — prokaryotic RNA polymerase consisting of α , β , and β ' but missing σ ; this complex performs elongation. genetic code — degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three nonsense codons.