MIP 302 Exam 2 Study Guide with Complete Solutions

MIP 302 Exam 2 Study Guide with Complete Solutions Virus - Answer️️ -A tiny, nonliving particle that invades and then reproduces inside a living cell. Viral Characteristics - Answer️️ -viruses are inert unless they are inside a living cell, viruses are acellular composed only of nucleic acid and protein shell. They also produce progeny virion inside a living host cell, possess genetic material that is passed from one 'generation' to another, they are also infectious agents Bacteriophage replication steps - Answer️️ -1. attachment of phage to host cell 2. penetration of the bacterial cell wall 3. Synthesis of phage nucleic acids and proteins 4. assembly of the phage particles 5. release of the phage particles animal virus replication - Answer️️ -1. attachment of the virus to the host cell 2. entry or uptake of the virus into the host cell 3. removal of the protein coat surrounding the virus 4. synthesis of viral nucleic acids and proteins 5. assembly of viral protein and nucleic to form progeny virions 6. release of the virions from the host cell ©SOPHIABENNETT EXAM SOLUTIONS Saturday, September 7, 2024 6:58 PM Page | 2 attachment - Answer️️ -the virus attaches to the host cell by means of a very specific receptor site. For this reason, viruses will infect only certain hosts, and often only certain cells in the particular host. Bacteriophage - Answer️️ -viruses that only infect bacterial cells entry - Answer️️ -bacteriophages essentially 'inject' their genetic material through the bacterial cell wall, while many animal viruses enter through endocytosis. Animal cells degrade foreign agents in an acidic lysosome. Sometimes the virus 'tricks' the cell by attaching to the receptor site for some compound utilized by the cell so the cell will not degrade it thinking it is a useful compound. Uncoating - Answer️️ -Endocytosis into a lysosome does not harm the virus. It only strips away the protein coat, allowing the viral nucleic acid to enter the cell and take over the cell machinery. Synthesis of Viral Nucleic Acids and Proteins - Answer️️ -Virus uses the cell to make viral proteins and nucleic acid. How depends on what type of DNA/RNA the virus has Assembly - Answer️️ -(viral morphogenesis) the encapsulation of the viral nucleic acid inside the protein capsid. This results in the formation of new, whole virions release - Answer️️ -viruses may either lyse the host cell or they can bud out (depending on envelope). The progeny virions attach to neighboring healthy cells and infect them viral cultivation - Answer️️ -requires the use of living cells in which virus can replicate. When enough bacterial cells have been infected and lysed, discrete holes or plaques ©SOPHIABENNETT EXAM SOLUTIONS Saturday, September 7, 2024 6:58 PM Page | 3 can be seen in the lawn of bacterial cells. Each plaque is considered to be the result of one phage or PFU Provide 2 reasons why bacteria were added to the agar deeps. - Answer️️ -1. the virus needs a host to infect 2. So we can "see" the virus and count it Why did the phages produce discrete plaques within the bacterial lawn, and not spread throughout the bacterial lawn and kill all of the bacterial cells? - Answer️️ -Since the agar is solid, the plaques cannot disperse because the virions released from the lysed bacterial cell cannot move through the agar and therefore only infect the cell directly adjacent Why was the 0.5ml of E. coli cells that was added to each of the soft agar deeps not taken into consideration when determining the final dilution of the phage. - Answer️️ - Because when calculating dilutions you take the volume of phage added. It doesn't have anything to do with the number of bacteria. If you had 43 plaques on a plate inoculated with 1 ml of a 10^-6 dilution of phage, how many plaques would you expect to see on a plate inoculated with 1 ml of a 10^-5 dilution of phage? - Answer️️ -PFUs/ml = 43 PFUs/(10^-6)(1.0ml) = 4.3x10^7 PFUs/ml #PFUs = (4.3 x 10^7 PFUs/ml)(1.0ml)(10^-5) = 430 PFUs You wish to make a 1/5 dilution of a sample. Only 10 ml pipet