Figure 1.

Virus quasispecies. A representation of mutation differences between DNA species (top panel) and an RNA virus quasispecies (bottom panel). Each line represents a portion of the genome, and each circle is a randomly-generated mutation. Each mutation will have a random effect, with most mutations being deleterious or neutral (dark circles), but with a small chance to disrupt targeted interactions by drugs, antibodies, or RNAi (white cirlces). In the DNA population on top, there is very little genetic variation, and thus it would be expected to have a nearly uniform phenotype in most environments. The RNA quasispecies on bottom however contains many unique random mutations, each of which will have an unknown effect. If the mutations happen to be in a gene targeted by a specific antibody or drug, then that virus could be resistant, and would be favored to multiply and increase its proportion in the quasispecies, creating a larger pool of resistant viruses.