BIOL 2P98 Lecture Notes - Lecture 15: Lysogenic Cycle, 1-Hydroxy-7-Azabenzotriazole, Retrovirus
19 Jan 2016
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Document Summary
Plating efficiency: the number of plaque-forming units is almost always lower than direct counts by electron microscopy. Temperate bacteriophages & lysogeny: some viruses always kill the host following infection, temperate viruses can alternate between two pathways: Lytic pathway: assembly of virions & lysis of host. Lysogenic pathway: virus genome is replicated in synchrony with host chromosome without killing host. Lysogeny can confer new genetic properties on the bacterial host cell: = lysogenic conversion, a cell harbouring a temperate virus = a lysogen. Linear, dsdna genome with complementary overhangs at either end: packed into cell as a linear model, then forms a circle, upon penetration of host cell, dna circularizes. If entering lysogenic state, dna integrates into e. coli chromosome using att site: requires lambda integrase (phage-encoded enzyme) Lambda lytic pathway: when entering into the lytic pathway, long, linear concatemers of viral, cut into genome-sized lengths at cos sites & packaged into phage, tail added & cell lysis to release virions.
