Homework 3 - Homework 3 1 Define virion capsid enveloped viruses and infection What is the difference between icosahedral and helical viruses A

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Homework # 3 1) Define virion, capsid, enveloped viruses and infection. What is the difference between icosahedral and helical viruses? A virion is the complete virus particle, consisting of nucleic acid and protein coat (and sometimes other materials). Capsid is the protein coat of a virus. Enveloped viruses contain a lipid bilayer membrane covering the nucleocapsid portion. The envelope usually contains glycoproteins, as well. Infection is the process by which a virion enters a cell. Isocahedral viruses are spherical in shape, while helical viruses are rod-shaped. 2) What is a PFU? Describe how the concentration of virions in a solution can be quantitated. A PFU is a plaque-forming unit. It results from infection and lysis of bacterial cells in a lawn by a bacteriophage. Each PFU results from one initial infection event. The area of infection can be visualized due to repeated rounds of infection of bacterial cells in the immediate vicinity by viruses released during cell lysis. Therefore, the concentrations of virions in a solution can be quantitated by performing serial dilutions and plating aliquots of the solution with added bacterial cells on an agar plate. After incubation, clear areas (plaques) appear on the plate, each plaque corresponding to an initial infection of one bacterial cell with a bacteriophage. The number of PFUs/ml can be calculated, taking into consideration the dilution factor and the volume of solution plated. 3)
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This note was uploaded on 03/18/2010 for the course BIOL biol121 taught by Professor Dsaofj during the Spring '10 term at UC Riverside.

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Homework 3 - Homework 3 1 Define virion capsid enveloped viruses and infection What is the difference between icosahedral and helical viruses A

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