Biology 1001A Lecture Notes - Lecture 2: Tomato Bushy Stunt Virus, Lytic Cycle, Lysogenic Cycle
1 Oct 2016
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Document Summary
Characteristics of viruses and why they are not generally considered to be alive . Not considered alive- infectious biological particles: not a cell; no cytoplasm enclosed by plasma membrane, cannot reproduce on own; depend on host cell for reproduction, lack metabolic system (no energy) Virulent bacteriophages: t-even bacteriophages (t2, t4, t6) that affect e. coli valuable in genetic studies. Divided into head (containing double strand molecule of dna) and tail (with recognition proteins at its tip that binds to host cell) Virulent bacteriophage- kill host cells during each cycle (lytic cycle) Temperate bacteriophage- enter inactive phase inside host cell and can be passed on to several generations of daughter cells before before becoming active and killing host (lytic-> lysogenic->lytic) Lytic cycle: phage attaches to host cell- lyzsozyme enzyme in viral coat digests hole in cell wall of host. *what makes the prophage active/enter lytic cycle: environmental signals (nutrients available, uv irradiation)
