Pitt BIOSC 1850 - Final Exam Study Guide (24 pages)

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Final Exam Study Guide



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Final Exam Study Guide

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Pages:
24
Type:
Study Guide
School:
University of Pittsburgh
Course:
Biosc 1850 - Microbiology
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BIOSC 1850 1ST Edition Final Exam Study Guide Class Average 47 5 Answers to Exam Questions 1 Genes code for proteins that change the polymerase In phage lambda the N protein accomplishes this In MS2 its genome is RNA The ribosomes have different access sites for different genes Unwinding the secondary structure opens it up for more genes 2 Viruses are classified by folds in capsid proteins alpha helices beta pleated sheets etc There are three groups of viruses a Icosohedral i Hepatitis HIV b Helical i Tobacco mosaic virus influenza c Complex i Phage lambda T4 Mu herpesvirus poliovirus 3 Pyocin small attacker functioning to poke holes in cell walls of bacteria It resembles a phage tail and is made by bacteria 4 T4 destroys host genome through the destruction of nucleotides upon initial infection allowing it to enter directly into the lytic cycle Phage lambda does not destroy the host genome instead it incorporated its genome into that of the host entering the lysogenic cycle Because destroying the host genome removes the option of the lysogenic cycle phage lambda does not destroy the host genome 5 Gene transfer agents package and injects chunks of DNA into other members of the same species 6 Circular permutation the DNA of host bacteria is circular Cutting the same DNA plasmid at different section results in a different linear form but with the same genes Based on the different cutting points of the plasmid there are different end points of the linear version of the DNA 7 Of all known sequences of ribosomal small subunit sequences chloroplasts and mitochondria come closest to those two bacterium This is evidence of the endosymbiotic theory 8 dsDNA lambda herpesvirus ssRNA ebolavirus influenzavirus dsRNA Phi6 9 This compound is a methylated nucleotide thymine This is important in the phage T4 life cycle because it prevents the viral DNA from being degraded by its host cell The methylation serves as protection 10 How mutations influence viral replication a Mutations in the N gene would prevent the virus from replicating b Mutations in the cII gene would cause the bacteriophage to enter the lytic cycle c Mutations in the bacterial proteases would cause the bacteriophage to enter the lysogenic cycle Phage Lambda o Double stranded linear DNA At both of the 5 ends there are 12 bases that hang off Sticky ends cos site circularizes the DNA into the host cytoplasm The phage DNA can then be inserted into the host chromosome o Has a tail o Enters the lysogenic then lytic cycle o Once incorporated into the host genome through the help of the cos sites N and Cro are the first proteins to be expressed N antiterminator extends the reading frames to which it s bound This results in high levels of transcription of the following proteins N Cro cIII cII cI O P Q Cro functions in DNA replication induces the lytic cycle It blocks the promoter regulating cI synthesis so that it is not synthesized o CIII protects cII from bacterial proteases through competitive inhibition The lysogenic cycle ensues Lysogenic cycle maintained by cI o O and P proteins initiate the replication of the phage chromosome o Q is an antiterminator allows for lytic proteins and the phage head and tail proteins o For the first few replications the lambda genome undergoes replication then switches to the rolling circle replication releasing a concatemer Phage T4 o Lytic cycle only o Double stranded DNA Terminally redundant Several units are recombined end to end to form a concatemer and cut at varying sites forming several different circular permutations o Shine Delgarno Sequence ribosomal binding site in prokaryotic mRNA located just upstream of the start codon Allows for translation of phage proteins o Has a tail o Phage T4 structures degrade the host genome and uses the nucleotides to build T4 DNA o Has a fast and accurate DNA copying mechanism with a unique repair mechanism Phage 6 o Three part segmented double stranded RNA genome o Lipid membrane surrounding its capsid o Can enter the lysogenic cycle but it very much prefers the lytic cycle o Attaches to host with its P3 gene The envelope fuses with the outer bacterial membrane using phage protein P6 P5 digests peptidoglycan The envelope is made from bacterial inner membrane o RNA dependent RNA polymerases catalyzes the synthesis of RNA from an RNA template Mu Phage o Double stranded DNA o DNA based transposition is used to integrate its genome into the host o Transposable element DNA sequence that can change its relative position within the genome of a single cell Can create mutations and change genome size Each time a transposable element is inserted copied in the genome the host cell replicates providing each cell with a ton of copies of the viral DNA MS2 o Single stranded RNA genome o Icosahedral no tail o Contains only 4 genes Maturation protein lysis protein shell protein and beta subunit of RNA replicase 180 copies of the shell gene first to be transcribed As the ribosomes move along these genes they disrupt the secondary structure of the RNA genome making the other genes available to be translated o Infects bacteria with the F plasmid MS2 s maturation protein attaches to the F pilus o Lysis occurs when sufficient amount of the lysis protein is translated Influenza Virus o Single stranded RNA genome Segmented Allows for reassortment of viral RNA if more than one virus attacks a host cell This causes an antigenic shift sudden change from one antigen to another RNA dependent RNA polymerase is injected into the host along with the viral genome Lacks a proofreading mechanism An error occurs about once per replication cycle Newly manufactured virions are mutants resulting in antigenic drift slow change in the antigens H N over time o Type A influenza is the most virulent to humans o Pleomorphic virion Both spherical and filamentous forms of envelope o 2 large glycoprotein on the outside of the viral envelope Hemagglutinin Mediates binding of the virus to target cells entry of the genome into the host 16 known subtypes o Neuraminidase Mediated release of progeny viruses from the host 9 known subtypes Targets of antiviral drugs Antigens to which antibodies can be raised Herpesvirus o Double stranded linear DNA genome o Enveloped icosahedral o Enters directly into the lytic cycle and sometimes the lysogenic cycle for latent and persistent effects Ebolavirus o Filovirus o Helical o Starts as headache progresses to nausea vomiting then bleeding both internal and through


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