An antigenic variation is the mechanism by which an infectious organism changes its surface proteins in favour of circumventing a host immune response.

An antigenic variation is the mechanism by which an infectious organism changes its surface proteins in favour of circumventing a host immune response.

The Phase Variation is the reversible ability of some bacteria to turn an and off the expression of genes coding for the surface antigens .

While the Antigenic Variation is the modification of the gene for an expressed surface antigen by genetic recombination with one of many variable unexpressed DNA sequences.

In this manner , the expressed surface antigen can assume many different antigenic structures

RNA genome of influenza virus is segmented in to 7 pieces. It has the unique property of undergoing two types of genetic variation ie antigenic drift and antigenic shift. In antigenic drift the antigenic variations are minor where genetic recombination take place between strains of two similar species whereas in antigenic shift the recombination take place between strains of dissimilar species leading to major antigenic variations and hence seasonal epidemics.

Causes antigenic diversity in pathogens that contribute to more virulence- adaptive system must account for new targets.