Biology 1202B Lecture Notes - Lecture 22: Chromosome, Lysogenic Cycle, Lytic Cycle
26 Mar 2016
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Biology 1202b lecture 22: viruses and retroviruses i. Infected 500 million people: 1/3 of world population, killed 20-50 million. 3-5% of world population: one of the deadliest natural disasters in human history. Small infectious agents which replicate inside the living cells of other organisms: dna or rna genomes, proteins coat surrounding, can infect animals, plants, bacteria and archaea. Not alive: dependent on host cells for function. Proteins coat repeating protein subunits: virus genome is small. Coat may be surrounded by envelope from host cell. Acquired as the virus passes through the host cell membrane. Although it may have a membrane, it is not a cell. Envelope contains host and viral proteins: aids entry into cells, can adapt by altering membrane proteins. Virulent bacteriophages: kill host cell every infection cycle. Temperate bacteriophages: may enter inactive phase, passed on to daughter cells. Phage is not mobile: must randomly collide with appropriate host cell. Phage enzyme lysozyme: digests hole in bacterial wall.
