Viruses, part 2

Bacteriophage Multiplication Lytic Cycle Ends with Cell lysis Death of host cell Lysogenic Cycle Viral Genome integrates into host chromosome Prophage viral DNA

Lytic and lysogenic Cycle: Attachment Phage attaches by tail fibers to host cell Penetration Phage lysozyme opens cell wall DNA is injected into cell Biosynthesis Replicate viral DNA Make viral proteins Maturation Assemble new virus particles Release Phage lysozyme breaks cell wall New virions are released Integration Viral DNA becomes prophage Cell divides like normal replicating prophage DNA while it reproduces

Putting the virus together Virus Multiplication Attachment Penetration (Uncoating) Biosynthesis Maturation Putting the virus together Release

Animal virus attachment/penetration Naked virus No envelope Binds to surface of host cell and injects its DNA (similar to bacteriophage) Envelope virus Membrane fusion Binds to receptors and envelope fuses with the host membrane Phagocytosis Virus particles taken in by endocytosis

Animal Virus Multiplication Attachment Penetration Uncoating Biosynthesis Maturation Putting the virus together Release

Biosynthesis and maturation Single stranded DNA DNA enters the nucleus First produce ds DNA in nucleus Replication – make more DNA Transcription in nucleus – make RNA Proteins made in the cytoplasm from mRNA Proteins transported to the nucleus Viruses assembled in the nucleus with single stranded DNA

Biosynthesis and maturation Double stranded DNA DNA enters the nucleus Replication and transcription in the nucleus Proteins made in the cytoplasm from mRNA Proteins transported into the nucleus Assembly of virus in the nucleus with dsDNA

Biosynthesis and maturation + strand RNA (sense RNA) Entry and stay in the cytoplasm Make – strand RNA with RNA dependent RNA polymerase - strand RNA serves as template for more + strand RNA + strand RNA serves as mRNA Makes mRNA in the cytoplasm Assembly in the cytoplasm Packaged with RNA dependent RNA polymerase

Biosynthesis and maturation - Strand RNA (antisense RNA) Entry and stay in the cytoplasm Make + strand RNA with RNA dependent RNA polymerase + strand RNA serves as mRNA and makes viral proteins in the cytoplasm + strand also serves as a template to make – strand RNA Assembly of virus in the cytoplasm Packaged with RNA dependent RNA polymerase

Biosynthesis and maturation Double stranded RNA Entry and stay in the cytoplasm + strand RNA serves as mRNA and makes viral proteins in the cytoplasm Makes RNA dependent RNA polymerase + strand also serves as a template to make – strand RNA - strand serves as a template to make + strand RNA Assembly of virus in the cytoplasm Packaged with RNA dependent RNA polymerase

Biosynthesis and maturation Retroviruses + strand RNA viruses Reverse transcriptase makes DNA from RNA in the cytoplasm Then DNA moves to the nucleus (negative) Single strand DNA enters the nucleus and makes double stranded DNA DNA makes mRNA in the nucleus RNA makes viral proteins in the cytoplasm Assembly in the cytoplasm Reverse transcriptase packaged with the virus

Animal Virus Multiplication Attachment Penetration Uncoating Biosynthesis Maturation Putting the virus together Release

Animal Virus Multiplication Release Naked viruses Lyse the host cell Kills the host cell Virus particles released can infect other host cells Enveloped viruses Merge with the host cell membrane Form an envelope around the virus The cell is not lysed and not killed Cell continues to produce more viruses