Question

What is meant by a shift and a drift mutation in viruses?

Answer 1

A permanent change in the sequence of nucleotides of the genome is called mutation, which results in altered or absence of corresponding protein synthesis. The viruses can change their genetic sequences due to their rapid rate of mutation.

Antigenic drift refers to the small changes in the gene sequences of the virus, which occurs due to the rapid viral replication over a course of the period. The antigenic drift results in the viruses with the same antigenic properties to that of the parent virus. Whereas the antigenic shift results in the production of the viruses with different antigenic properties from the parent virus. Influenza viruses can undergo both the antigenic drift and antigenic shift changes.

The influenza virus can infect various animal species, i.e. humans, pigs, and birds. So, the viruses from these animals can infect the same cell. If this happens, the RNA (ribonucleic acid) segments of the virus uncoat and get mixed in the cytosol, which will re-sort and form a new genome for the influenza virus with a new hemagglutinin gene. This mixing process of RNA segments is called, “antigenic shift.” This large antigenic shifts generally occurs for every 10-15 years.