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Pitt BIOSC 1850 - Final Exam Study Guide
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BIOSC 1850 1ST Edition Final Exam Study GuideClass 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 genes2. 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. Helicali. Tobacco mosaic virus, influenza, c. Complexi. Phage lambda, T4, Mu, herpesvirus, poliovirus3. 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 species6. 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 thesame 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, herpesvirusssRNA: ebolavirus, influenzavirusdsRNA: Phi69. 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 byits 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 cyclec. Mutations in the bacterial proteases would cause the bacteriophage to enter the lysogenic cycle- Phage Lambda (λ)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 hostcytoplasm. 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 followingproteins: 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 andtail proteins o For the first few replications, the lambda genome undergoes Θ replication, then switches to the rolling circle replication, releasing a concatemer - Phage T4o Lytic cycle onlyo 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 DNAo Has a fast and accurate DNA copying mechanism with a unique repair mechanism - Phage Φ6o Three part, segmented double stranded RNA genomeo Lipid membrane surrounding its capsid o Can enter the lysogenic cycle, but it very much prefers the lytic cycleo Attaches to host with its P3 geneo 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 froman RNA template - Mu (Μ) Phageo Double stranded DNAo 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- MS2o Single stranded RNA genomeo 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 Viruso 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 timeo Type A influenza is the most virulent to humans o Pleomorphic virion  Both spherical and filamentous forms of envelopeo 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 Neuraminidase- Mediated release of progeny viruses from the host - 9 known subtypes  Targets of antiviral drugs Antigens to which antibodies can be raised - Herpesviruso Double stranded linear DNA genomeo Enveloped icosahedral o Enters directly into


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Pitt BIOSC 1850 - Final Exam Study Guide

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