Viruses

This week in AP Biology we talked about viruses. Viruses are very tiny and there genomes can be double or single stranded DNA or double or single stranded RNA. Viruses have a capsid which is a protein shell that surrounds the genetic material. Some viruses have viral envelopes that surround the capsid and aid the viruses in infecting their hosts. A type of bacteria we studied the most was bacteriophages or phages. They are viruses that infect bacterial cells. Viruses can only replicate in host cells which means they can infect limited variety of hosts. There are two viral reproductions. One is called the Lytic cycle and the other is the Lysogenic cycle. The lytic cycle ends in the death of the host cell by rupturing. Bacteriophages injects its DNA into a host cell and takes over the host cell's machinery to synthesize new copies of the viral DNA. In the lysogenic cycle the bacteriophage's DNA becomes incorporated into the host cell's DNA and is replicated along with the host cell's genome.