MICRO EXAM 2 Studyguide
MICRO EXAM 2 Studyguide Micro 2123
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This 4 page Study Guide was uploaded by Meredith McKnight on Thursday September 15, 2016. The Study Guide belongs to Micro 2123 at Oklahoma State University taught by Noha H. Yousseff in Fall 2016. Since its upload, it has received 71 views. For similar materials see Introduction to Microbiology in Microbiology at Oklahoma State University.
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Date Created: 09/15/16
Study guide for Exam 2 Chapter 7 • DNA structure – N-base: A=T and CΞG (number of bonds)f Phosphate, deoxyribose sugar, – Phosphodiester bonds versus H bonds – 2 strands are complementary – 2 strands are anti-parallel • In the cell, DNA is packed supercoiled, topoisomerases help to or supercoiling.\ • Replication=making copies of the genome • Stages: initiation at ori sites, elongation making the replication bubble (actual copying happens), termination at ter sites • Replication is semi-conservative. Know what this means. • Leading strand copied continuously, lagging strand copied in fragments called Okazaki fragments. This is because the RNA polymerase can only add nucleotides to the newly made starnd in the 5’ to 3’ direction • Enzymes: helicase, primase, DNA polymerase, ligase. Know what each one does. Chapter 8 • Transcription=making mRNA from DNA template • RNA is also made of nucleotides but – It is singe stranded – Sugar is ribose – U instead of T • Star enzyme is RNA polymerase (made of core polymerase + sigma factor) – Initiation: sigma factor binds to gene promotor – Elongation: transcription bubble (actual copying happens here) – Termination: Rho-dependent or independent • Transcription=making mRNA from DNA template • RNA is also made of nucleotides but • It is singe stranded • Sugar is ribose • U instead of T • Star enzyme is RNA polymerase (made of core polymerase + sigma factor) • Initiation: sigma factor binds to gene promotor • Elongation: transcription bubble (actual copying happens here) • Termination: Rho-dependent or independent • Transcription and translation are coupled • Translation=making protein from mRNA • Translation requires: – Template=mRNA, carry the code. Each 3 nucleotides=1 codon. 64 codons total; 61 specify aa and 3 specify a stop codon. Genetic code is UNIVERSAL and REDUNDANT. – Ribosomes (made of a small subunit and a large subunit). When they come together they form 3 pockets (A, P, and E sites) for tRNA – tRNA molecules that carry the aa. tRNA has 2 functional regions; an anticodon, and the aa binding site. Chapter 9 • Transformation: free DNA uptake, requires recipient cells to be COMPETENT • Conjugation: plasmid DNA uptake, requires cell-to-cell contact. Donor has sex pili. • Transduction: bacteriophages carry DNA from one host to the next. • Why do cells uptake DNA? • HGT increases competitiveness or food • The cells have devised a mechanism to selectively degrade incoming DNA if it does not want it. Restriction endonucleases (RE) are enzymes that can degrade DNA. cells protect their own genome from the effect of RE by protective methylation • Incoming DNA can be • Degraded by RE restriction endonucleases. • Or integrated in the genome by recombination • Mutations: Point Vs insertion/deletion mutation • Silent, missense, nonsense, frameshift. Know the difference • Repair mechanisms: • BER: removes 1 damaged base and replace with undamaged one • NER: removes 12-13 nucleotides including the damaged one then replaces them with correct undamaged nucleotides • MMR: removes undamaged but mismatched nucleotides. Recognizes the methylation pattern in DNA to know which strand to use as template. Chapter 10 • Control of gene expression 5 levels 1. DNA level: mutate gene most drastic least reversible 2. Transcription level: activators/repressors, and also modify the activity and conc of sigma factors 3. Post-transcription level: modify mRNA stability by Rnases 4. Translation level: translation repressor proteins 5. Post-translation level: modify the protein after it is made by chemical modification or cleavage. 2-component signal transduction: 2 proteins; one is membrane spanning and sense the external environment, and the other is cytoplasmic and modulate gene expression. Chemotaxis: bacteria move towards favorable conditions or away from harsh conditions. By flagellar rotation; counterclockwise it swims forward, clockwise it tumbles away. Quorum sensing: bacteria work together at high cell density. They secrete an extracellular autoinducer (AI) molecule. At a certain threshold, the AI re-enters the cell and modulate gene expression
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