Gene
Sequence of nucleotides in DNA molecule
Codes for 1 polypeptide
Nucleotide order determines amino acids
Nucleotides (triplet codons) and amino acids relationship is genetic code
Same code by nearly all living organisms, near-universal
20 amino acids, 4 nucleotide bases
If 1 base coded for 1 amino acid, only 4 amino acids have codes (4^1 = 4)
2: 4^2 = 16
3: 4^3 = 64; too many?
Each has more than one codon; degenerate
Some triplets “full stops”, indicating gene end
Non-overlapping code
Each base read once
