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Lecture 24

BSCI 283 Lecture Notes - Lecture 24: Lysogenic Cycle, Exonuclease, Endonuclease


Department
Biological Sciences Program
Course Code
BSCI 283
Professor
Daniel Stein
Lecture
24

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21st Century Health 5/8/17
Viruses
o Viral growth is exponential compared to bacterial
o Plaque assay must have controls
o Number of plaques stays the same
o Failure to bind shows cell is not susceptibledetermine host range
o Eclipse-pfu goes down as viral particles are adsorbed before new particles are
made and released into supernatant
o Virus is replicated
o Burst size-difference between starting and after 1 replication
o Black line-virus is adsorbed but no viral productionmay be integrated into
nucleic acids to become lysogenic or cell defeated virus
Bacteriophage Replication
o Lytic cyclehost cell is lysed
o Lysogenic cyclegenotypic change if genes are expressed
o phenotypic change
o By activating genes can mess up cell communication or cause cancer
o Geotpic chage does’t have to relate to pheotpic chage
o Generalized transduction-mistake in virion assembletransfer bacterial genes
o Specialized transduction-mistake in excision, transfer to second cell
o All bacteria have nucleases that attack DNA and RNA
o Eoucleases attack free 5; or 3’ eds of DNA, RNA olecules
o Endonucleases (restriction enzymes) cleave DNA at specific sequences
o Host cell DNA protected by methylation of a base in this sequence
o Viral DNA not methylated, not protected
o Cell surfaces possibility of mutation to alter receptor
o Can become resistant by preventing virus from attaching to cells
HIV
o Envelope structure
o Glycoproteins
o Vial capsid and nucleic acids
o Virally encoded proteins inside
o Viral capsid
o Infect CD4T cells which have receptors necessary for function
o Virus interacts only with CD4T cells because express receptor
o Cell changes surface to bring virus from outside to inside- phagocytosis
o When virus binds tight enough- fuses with membranereleases capsid into cell
o Viral capsid cannot stabilizedisintegratesRNA and proteins (reverse
transcriptase) released
o Reverse transcriptase converts RNA to DNA should be in nucleuscell brings in
o Either integrated into CD4T cell nucleuslysogenic
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