Final answer:
A plaque in viral growth is a clear area on a bacterial lawn resulting from cell lysis due to viral infection, starting from a single virus particle. It allows for the quantification of viral titer and study of viral behavior and antibody effectiveness.
Step-by-step explanation:
In the context of viral growth, a plaque refers to a clear area on a bacterial lawn caused by the lysis of host cells due to viral infection. When a virus infects a cell within a lawn, it replicates within that cell until the cell bursts open (lysis) and releases new virus particles. These particles then infect neighboring cells, and the process repeats, leading to a growing area of dead cells that can be visually identified as a plaque. Each plaque originates from a single virus particle and represents the viral replication and destruction of host cells in that zone. This method is widely used for quantifying the number of viruses (viral titer) in a sample.
Researchers use plaques to study various aspects of viral behavior, including the rate of spread, mutation effects, and the effectiveness of antibodies in preventing viral entry into host cells. For instance, a plaque reduction assay can measure antibody responses by determining the dilution level at which antibodies in a serum sample can neutralize 50% of the virus, thus reducing the number of plaques formed.