Transcription and manufacture of capsid proteins Self-assembly of new virus particles and their exit from the cell Entry and uncoating VIRUS 1 2 3 DNA Capsid 4 Replication HOST CELL Viral DNA mRNA Capsid proteins Viral DNA Viruses use the host’s cellular machinery to reproduce itself enzymes, ribosomes, tRNAs, amino acids, ATP, and other molecules
Fig. 19-6 Phage DNA Phage The phage injects its DNA. Bacterial chromosome Phage DNA circularizes. Daughter cell with prophage Occasionally, a prophage exits the bacterial chromosome, initiating a lytic cycle. Cell divisions produce population of bacteria infected with the prophage. The cell lyses, releasing phages. Lytic cycle is induced or Lysogenic cycle is entered Lysogenic cycle Prophage The bacterium reproduces, copying the prophage and transmitting it to daughter cells. Phage DNA integrates into the bacterial chromosome, becoming a prophage. New phage DNA and proteins are synthesized and assembled into phages.
Glycoprotein Reverse transcriptase HIV RNA (two identical strands) Capsid Viral envelope HOST CELL Reverse transcriptase Viral RNA RNA-DNA hybrid DNA NUCLEUS Provirus Chromosomal DNA RNA genome for the next viral generation mRNA New virus The viral DNA that is permanently integrated into the host genome is called a provirus (unlike prophage)
HIV Membrane of white blood cell HIV entering a cell 0.25 µm New HIV leaving a cell