Gene Expression

Protein Synthesis

The sequence of nucleotide bases on a gene provides a code that is an instruction for a protein that is built through transcription and translation. This is the basis of the ‘one gene one polypeptide’ hypothesis such as coding for:

•Structural proteins (keratin and collagen)

•Haemoglobin

•Immunoglobulins (antibodies)

•Cell surface receptors

•Antigens

•Actin and myosin (form muscle)

•Channel proteins

•Electron carriers

•Enzymes

The genetic code is a triplet codon. Three nucleotide bases code for one amino acid. The number of different triplet sequences are 43 or 64.

The code is non-overlapping, as each base is part of one codon.

It is also degenerate, where different codons code for the same amino acid.