But when the virus produces protein, a troublesome mutation results in a change to the amino acid sequence that makes up the protein.

ECONOMIST: Viruses: Hunt the mutant | The

Both rely on having a protein's amino-acid sequence in the bag, and both have strengths and weaknesses.

ECONOMIST: REPORT: PROTEOMICS: After the genome | The

The tag is a particular sequence of the amino-acid units of which all proteins are composed.

ECONOMIST: The 1999 Nobel prizes