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MICR 271 FINAL EXAM QUESTIONS AND COMPLETE ANSWERS.
Typology: Exams
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Replisome Speed - answer eukaryotic slower - must displace nucleosomes, cell-dependent regulation of replication multiple initiation sites to compensate Bacterial Replication Forks - answer 1. Helicase unwinds DNA, lagging strand coated with single stranded binding proteins, RNA primer synthesized by primase
Translesion Repair - answer insert bases opposite damaged nucleotides or repair dsDNA breaks Class I virus - answer dsDNA genome mRNA synthesis: transcription using host machinery, translatin mRNA --> proteins genome replication: using host machinery Class II virus - answer ssDNA genome (+ or -) mRNA synthesis: dsDNA transcribed into mRNA using host machinery genome replication: dsDNA produced and replicated, strands separated Class III virus - answer dsRNA genome mRNA synthesis: separated into ssRNA, + strand used as mRNA, translated into viral proteins genome replication: + ssRNA = template to produce new dsRNA Class IV virus - answer + ssRNA genome mRNA synthesis: + ssRNA used as mRNA, translated into proteins genome replication: + ssRNA used to produce - ssRNA = template to produce new + ssRNA Class V virus - answer - ssRNA genome mRNA synthesis: -ssRNA template to make + ssRNA (mRNA) translated into proteins genome replication: -ssRNA used to produce + ssRNA = template to produce new -ssRNA Class VI viruses - answer Retroviruses ssDNA reverse transcribed from RNA genome, dsDNA made using DNA Pol mRNA synthesis: dsDNA integrated into host genome --> mRNA --> protein genome replication: + ssRNA --> ssDNA by viral reverse transcriptase --> dsDNA into host genome by integrase --> +ssRNA to produce new genomes Class VII viruses - answer Reverse transcribing dsDNA genome mRNA synthesis: dsDNA --> mRNA by viral RNA Pol --> proteins
Factor Independent Release: mRNA forms stem-loop structure, RNA Pol falls off Factor Dependent Release: Pol pauses at end of coding region, interacts with Rho factor causes Pol to fall off Polyribosomal Complex - answer structure formed when coupling transcription + translation only in bacteria (no nucleus) Protein Synthesis - Initiation - answer 1. initiation factors (IFs), GTP, fMet-tRNA^fMet and 30S subunit assembles with mRNA
e.g. nucleoid associated proteins enhance or prevent access to DNA Post-Transcriptional Control of Gene Expression - answer control through mRNA modifications e.g. splicing in eukaryotes Translational Control of Gene Expression - answer control frequency and speed mRNA transcripts translated at e.g. secondary structure in 3' mRNA prevents transcript degradation e.g. small RNA binding to mRNA affects translation initiation Post Translational Control of Gene Expression - answer contorl rate protein becomes active/funcitonal e.g. phosphorylation, dephosphorylation Agonist: binds and activates receptor Antagonist: binds and blocks receptor Class I Bacterial Transcriptional Activator - answer activator protein associates upstream
microRNA + RISC protein, helps present to target mRNA Outcomes:
Antibiotics targeting 30S subunit - answer antibiotic interaction sites clustered along path mRNA and tRNA interactions Antibiotics Targeting 50S subunit - answer most antibiotic interaction sites clustered at or near peptidyl-transferase centre (PTC), where peptide bond formation occurs Streptomycin and Tetracycline - answer interfere with tRNA delivery Chloramphenicol and Clindamycin - answer inhibit peptide bond formation by preventing correct amino acid positioning of aminoacylated tRNA's in PTC Erythromycin - answer inhibits elongation by interfering with aminoacyl translocation Aminogycosides - answer interfere with peptide elongation = misreading of mRNA truncated proteins Puromycin - answer inhibits terminatino Mechanisms of Resistance to Ribosome targeting antibiotics - answer 1. impaired drug efflux due to low membrane permeability
polycistronic Tat - answer binds stem-loop at 5' viral RNA, activates viral transcription by stimulating elongation starting at viral long terminal repeat Rev - answer transports mRNA encoding viral structural proteins form nucleus to cytoplasm, increasing rate proteins synthesized Translational Control HIV and other viruses - answer 1. multicistronic transcripts (optimal translational control with small genome)
Rhizosphere - answer soil region directly influenced by root secretions + associated soil microorganisms Commensal Microbes - answer derive benefit without hurting or helping plant Pathogenic Microbes - answer damage plant by infection or production phytotoxic compounds Beneficial Microbes - answer promote plant growth or protection Kudza Bug - answer feed on capsules of organisms that will live in bug as symbiont when born, if not present goes looking suggests --> animal behaviour shapes symbiont acquisition Green Iguana - answer young iguanas eat soil and feces to tailor microbiota suggests --> animals may adjust microbiota at different life-history stages Bobtail Squit - answer ejects bioluminescent bacteria daily suggests --> animals can actively control symbiont populations Fruit Fly - answer diet specific microbiota influence mating preferences
Sessile - answer surface-attached Mixed Species Biofilm Formation - answer 1. commensal organisms form biofilm, AI secretions low for intraspecies communications
oral + nasopharyngeal flora established within hours of birth, lower intestine within 1 day delivery (vaginal/C-sec), diet (breast milk/formula), gestational age, sanitation, antibiotic treatment influence flora Commensal Fungi - answer problematic when colonize new areas body --> new niche = high growth level = immune response skin: few species, many on feet internal: on mucosal surfaces, many types Normal Fungi - answer small component of commensal flora health contribution unknown normal fungi change more than normal microbiota (due to envirnoment) prolonged antibiotic treatment = predispose fungal infections Viruses as Commensals? - answer body can harbour persistent viral infection may protect or predispose person to infections