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Microbiology exam #2
Chapters 9,6,11,12
| Term | Definition |
|---|---|
| Three basic parts of a nucleotide are | Phosphate deoxyribose sugar nitrogenous base |
| The 2 strands of DNA are joined to each other or held together by | hydrogen bonding |
| Which of these are base paired correctly? C-T C-A G-T T-A | T-A |
| The 2 strands of the DBNA molecule are | antiparallel |
| The specific point on the DNA molecule where replication begins is the | origin of replication |
| Early in the process of DNA replication, the enzyme________ separates the 2 strands | helicase |
| DNA polymerase | requires a template for the synthesis of DNA can only add nucleotides in a certain direction |
| If an organism lost the ability to make primase, what would it be unable to do? | add a short sequence of complementary RNA to the existing DNA strand |
| Two different mechanisms for copying the DNA strands are used because | the strands are oriented in opposite directions |
| On one of the strands of bacterial DNA, the new complementary strand is synthesized discontinuously into small pieces of DNA called | Okazaki fragments |
| One bacterial chromosome replicates to become 2 chromosomes with | each made of one strand of DNA from the original chromosome and one newly synthesized strand |
| A segment of DNA encoding a protein or an RNA molecule is a | gene |
| A __________ is the physical expression of the genes present and can change depending upon what genes are turned "on" | phenotype |
| Which nitrogenous base is NOT present in RNA | Thymine |
| Both DNA and RNA are usually double stranded molecules | FALSE |
| The process of synthesizing RNA from a DNA template is _____ | transcription |
| The initial transfer RNA occupies the _____ on the ribosome | P site |
| _________ are groups of 3 bases in mRNA that specify one amino acid in the amino acid chain | Codons |
| If the codon GGU is positioned in the A site of the ribosome, what will occur? | a tRNA with the anticodon CCA will deliver its amino acid to the site |
| What usually terminates the process of translation | presence of a stop codon on mRNA |
| The bond connecting amino acids is a _________ bond | peptide |
| If you know the sequence of nucleotides in mRNA, you can deduce the DNA sequence it was transcribed from | True |
| What depicts the direction genetic info flows? | DNA--->RNA--->protein |
| Protein synthesis occurs on | ribosomes |
| Replication, transcription and translation take place in the bacterial cytoplasm | True |
| RNA is a chain of | nucleotides |
| What three components make up RNA structure? | phosphate, nitrogenous base, ribose sugar |
| What component of RNA is different from one individual or one bacterium to the next? | order of nitrogenous bases |
| The purpose of RNA synthesis is to provide a new copy of DNA as the original strand deteriorates over time | False |
| Transcription begins when RNA polymerase binds to __________ | promoter on DNA |
| If one strand of DNA contains the bases ACAGT, what would be the complementary bases on the mRNA strand | UGUCA |
| Synthesis of mRNA is | in the 5' to 3' direction with new nucleotides being added to the 3' end of mRNA molecule |
| What happens when a hairpin loop forms in mRNA? | the RNA polymerase and the mRNA dissociate from the DNA |
| The process of transcription is similar to | the synthesis of the leading strand during DNA replication |
| After mRNA is made, what generally occurs? | the mRNA is translated to protein |
| Unlike DNA, RNA is usually single-stranded. | True |
| The classic transformation experiment done by Griffith used | harmless and virulent strains of Streptococcus pneumoniae |
| Transformation is a form of recombination. Recombination is__________ | one bacterium donating DNA to another |
| In addition to transformation, the other 2 forms of horizontal gene transfer or recombination are | conjugation and transduction |
| In the beginning of transformation ________ binds to the target cell | double stranded DNA |
| During the entry of the donor DNA into the recipient cell | one strand is broken down by nucleases |
| The donor DNA | pairs with a homologous region o the recipient DNA |
| Mismatch repair is activated by | any difference between nucleotide sequence in the donor and recipient DNAs |
| As a result of mismatch repair during transformation | cells may have either original DNA or donor DNA in them |
| During the process of transformation in the lab setting, cells are plated on selective media to | make sure that only transformants grow |
| Cells that are capable of bringing DNA from their environment in through their cell wall are called | competent |
| Transformation is facilitated by | proteins on the cell wall that bind DNA from the environment |
| Central Dogma (newer version) | While information primarily flows from DNA to RNA to protein, some info from RNA flows back to DNA in a regulatory role |
| An operon is composed of ________ | DNA |
| All structural genes in an operon code for proteins related to the same function | TRUE |
| Which part(s) of an operon will eventually be translated to protein? | Structural genes |
| If lactose is present, the operator of the lac operon is switched ____________ therefore, this is an example of a(n) ______operon. | on, inducible |
| Of all infectious agents, which group has the most variety of drugs designed to treat infections? | Bacteria |
| Antibiotics would be effective against which of these infections? | Cholera genital warts whooping cough syphillis |
| Why do antiviral medications often have side effects? | Viruses are intracellular pathogens, and therefore there is often host cell damage with antiviral treatments. |
| Rather than developing more antiviral medications, what is a more common focus for researchers when it comes to viral diseases? | vaccine development |
| virus size large to small | E. coli streptococcus Rickettsia Mimivirus Rabies Adenovirus Yellow fever |
| multiplication cycle of RNA animal viruses | Adsorption penetration-virus engulfed into vesicle uncoating-viral envelope is shedded synthesis assembly release |
| unique characteristics of viruses | -while viruses are not considered living, they cannot direct own multiplication but can direct the behavior of living cells -have a nucleic acid genome, can be RNA or DNA, SS or DS -species-specific and infect cells from all 5 kingdoms |
| During replication of the positive sense strand of lytic RNA phage, in order to make more positive | -the + RNA strand must code for the synthesis of RNA polymerase -RNA replicase uses the + sense RNA as a template to make -strand RNA -the - sense strand RNA is used to make more + strands |
| The negative sense strand of RNA is_____ | used to synthesize more + strands |
| A positive sense strand lytic RNA phage attaches to the cell wall of an E. coli bacterium | False |
| Phage induced lysozyme lyses the host cell releasing the newly made phage | True |
| A positive strand of RNA | can directly act as mRNA |
| Steps to the lytic cycle | adsorption penetration synthesis assembly Lysis |
| How are temperate phages replicated? | The phage is replicated along the host cell's genome |
| An infection in animals similar to a lysogeny in bacteria is called a ___________ infection. | persistent |
| The activation of a prophage to enter the lytic cycle is called _________. | induction |
| Both lytic and lysogenic cycles eventually lead to bacterial host cell damage | True |
| How does lysogeny affect humans | Bacteria can become virulent due to phage genes, causing greater damage to infected human host |
| Possible configurations of viral nucleic acids | single stranded DNA Double stranded DNA-linear double stranded DNA-circular |
| Microbial control methods-Physical | heat and radiation |
| microbial control methods-mechanical | filtration |
| microbial control methods-chemical | surfactants halogens- ex: chlorine ---> which is sporicidal H2O2---> high activity-sporicidal phenolics--->ex: carbolic acid alcohols heavy metals-->ex: silver---> which is oligodynamic-sm amounts |
| halogens | Chlorine Iodine- ex: betadine, penetrates cells and interferes w/protein synthesis, can also be extremely irritating to the skin and toxic when absorbed |
| Hydrogen peroxide | -3% solution is used as an antiseptic for skin and wound cleansing -can be sporicidal in high concentrations -highly toxic to cells because of free radical formation |
| ethylene oxide | used to disinfect delicate instruments and plastic materials |
| Phenolics | Triclosan is a member of this antimicrobial category |
| Chlorhexidine | -used in hand scrubs, prepping skin for surgery -targets cellular membranes and denatures proteins -popular hospital agent due to low toxicity and rapid action -limited variable effects on fungi and viruses |
| aldehydes | VERY TOXIC, but used to disinfect surgical instruments |
| alcohol | -a 70% solution is best for denaturing microbial proteins -evaporates quickly which lowers effectiveness -ex: ethyl and isopropyl -dissolves membrane lipids and decreases surface tension |
| detergents | disrupt cell membranes but only rated for low level disinfection |
| heavy metals | mercury and silver |
| The effectiveness of a particular microbial agent is governed by several factors besides _____ | time |
| The _______ of microbes affects the action of an agent, as does _______ of the population. | Number composition |
| The ________ as well as the ______ level of the environment will also influence the action of microcidal agents | temperature pH |
| The __________ of the agent as well as the _______________ against microbes also play a role in its ability inactivate microbes | concentration mode of action |
| the presence of ________ matter, such as saliva and blood also inhibits the action of many microbicidal agents | organic |
| relative resistance of different microbial types from more to less | Protons bacterial endospores mycobacterium staphylococcus and pseudomonas protozoan cysts protozoan trophozoites most gram - bacteria fungi and fungal spores non enveloped viruses most gram + bacteris enveloped viruses |
| The use of radiation as a microbial control mechanism | -use of rad. to control microbial growth comes in 2 form ionizing and nonionizing. ionizing is most destructive -nonionizing rad, ex UV light causes electrons to mk a quantum leap to orbital w/ higher energy state, cause thymine dimers to form, no ions |
| destruction of ALL microbial life | Sterilization |
| destruction of most microbial life on inanimate surfaces | disinfection |
| destruction of most microbial life on living tissue | antisepsis |
| mechanical removal of most microbes from living or inanimate surfaces | decontamination |
| A chemical labeled as bactericidal will kill bacteria where as a chemical labeled as bacteriostatic will inhibit bacterial growth but will not kill them | true |
| Conjugation | donor-living cell w/f factor recipient- living F-cell direct 2 cells transfer DNA through hollow appendages |
| transformation | donor- Lysed cell recipient- living competent cell indirect naked DNA is taken up through cell boundary |
| transduction | donor-dead cell lysed by phage recipient-living cell infected with phage indirect but with a vector Bacteriophage transfers DNA between host cells |
| agents that will kill a microbial pathogen or completely inactivate its ability to cause disease | virucide germicide sporicide |
| betadine belongs to what group of chemical control agents | halogens |
| major cellular target of chemical antiseptics and disinfectants | cell wall synthesis of proteins and nucleic acids cytoplasmic membrane cytoskeleton is NOT |
| sterile saline has sterilizing effects on the skin | false |
| DRY heat control of microbes | more time is required -incineration ---> temps can reach 6000 degrees C -oven----> sterilization takes 4 hours |
| MOIST heat control of microbes | less time required -non-pressured steam -boiling water---> disinfection---baby bottles and food -pasteurization--->beverages----71.6 C for 15 seconds -steam under pressure--->15 psi--- sterilizes on least time |
| Salting of meat prior to the development of refrigeration technology was an example of using osmotic pressure to control microbial spoilage of this food product | true |
| mechanism of drug resistance | drug inactivation--> drug is changed decreased permeability--> drug can't ding its target drug pumps---> drug enters but doesn't stay alternate metabolic pathway---> drug binds correctly |
| Inhibition of virus entry | no infection |
| Inhibition of nucleic acid synthesis | no viral DNA synthesis no reverse transcription |
| Inhibition of viral assembly/release | no virions leave host cell |
| The goal of antimicrobial therapy is to deliver a drug that will destroy the _______ without harming the _______ | pathogen host |
| An ideal antimicrobial drug is _________ rather than ____________ and is relatively soluble. | microbicidal microbiostatic |
| An ideal drug remains potent long enough to act, but does not lead to the development of ____________ in microbial populations. | antimicrobial resistance |
| An effective drug assists the host's ______ and should not cause ______ or other infections. | defenses allergies |
| An ideal drug should be readily delivered to the site of _________ in the host and overall the drug should be reasonably ________. | infection priced |
| methods of antimicrobial susceptibility testing that can be used to determine minimal inhibitory concentration (MIC) | Etest Tube dilution test |
| Antibiotics other than Beta-lactam drugs, that also inhibit bacterial cell wall synthesis | vancomycin Isoniazid Bacitracin |
| Viruses are able to multiply inside a non-living cell | False |
| Individual viral particles have only one type of nucleic acid | True |
| Cells that lack compatible virus receptors are resistant to infection by that virus | True |
| What is the function of the reverse transcriptase enzyme | synthesizes DNA from RNA |
| superinfection | occurs due to the overgrowth of other potentially pathogenic microbes during or after initial antimicrobial therapy |
| drugs that are designed against which target are likely to have the least selectivetoxicity | cell membrane |
| antimicrobial that has the broadest spectrum of activity | tetracycline |
| your microbiome is most susceptible to changes when taking a _______ spectrum antimicrobial | broad |
| Which microbial group is the easiest to selectively target with antimicrobials | bacteria |
| BAsed on Kirby Bauer testing, a microbe is susceptible to antibiotic X and Y. X has Therapeutic Index 10 and Y Index of 3. Which would be the best choice based on the info given? | Antibiotic X |
| Bacteria have as much genetic information as Eukaryotes | False |
| PLasmids are necessary for the metabolism of bacteria | False |
| What are the main types of plasmids? Why are they medically relevant? | F plasmids transferred through F pilus R plasmid for resistance important for antibiotic resistance |
| DNA replication in prokaryotes is bidirectional, whereas in eukaryotes it is not | True |
| Bacteria have _____ origin of DNA replication, whereas eukaryotes have ________ | 1 multiple (bubbles) |
| What enzyme uses complimentary binding to replicate DNA? RNA? | Polymerase |
| Making mRNA from DNA template is called _________ whereas using tRNA, and ribosomes to make mRNA into a chain of amino acids is called _______ | transcription translation |
| Prokaryotic mRNA is _________, meaning that many genes are transcribed and translated at once. | polycistronic |
| Bacteria utilize alternative splicing in their cells to create alternative versions of proteins. | False |
| Every species on earth essentially uses the same genetic code for codon ----> amino acid pairing | True |
| Bacterial transcription and translation is more efficient than in eukaryotes | Don't want interruption of our cells |
| Antibiotics that interrupt bacterial protein synthesis can also affect eukaryotic cells | False, can make multiple transcriptions |
| What are the three important features of an operon? | promoter operator structural genes |
| What event triggers induction of the lac operon? | lactose |
| The presence of tryptophan represses the trp operon | True |
| Describe the difference between an inducible and a repressible operon | inducible is turned on repressible is turned off |
| What is the difference between positive and negative regulation? | positive is controlled by an activation and negative is controlled by a repressor |
| What are the three ways that bacteria horizontally share genes? | Bacterial transformation bacterial transduction bacterial conjugation |
| What is the difference between F factor transfer and Hfr transfer? | F-pilus complete genome oilus Hf is interrupted before DNA transfer |
| A cell must be ________ in order to be transformed. | competent |
| A bacterium is considered a recombinant if it has new genes, even if they aren't expressed | False |
| __________ are involved in transduction. | Bacterial phages |
| ___________ transduction involved the transfer of one specific gene, not a random one. | specialized |
| What is a pathogenecity island? | stretch of genes that pass on to be pathogenic |
| A spontaneous mutation arises from exposure to chemicals or physical agents | True |
| A ______________ mutation results in a stop codon and a nonfunctional protein. | nonsense |
| Mutations are always harmful to organisms | False |
| Mutations, once they happen are permanent | True |
| On an evolutionary scale, why are mutations and genetic diversity important? | mutations are changes to an organism's DNA and are important driver of diversity in populations mutation has introduce a new allele into the population that increase genetic variation and may be passed on to the next generation |
| Viruses can be seen with a light microscope | False |
| Viruses are alive | False |
| Viruses have no internal ______________, and are instead simply infectious particles that contain, at minimum, __________ and ______ | metabolic process nucleic acid proteins |
| Viral infections are more common than bacterial infections | True |
| Viral mutation rates are low and viruses are easy to track in a population | False |
| Viral capsids are constructed from ________ subunits | capsomers |
| What shapes do capsids come in? | complex helical isocahedral |
| List 3 forms of viral nucleic acid | dsDNA ssRNA ssDNA |
| What is an envelope? | surrounds the capsid and is part of the membrane |
| Standard virus classification systems use the following: | genetic makeup structure disease caused |
| A virus name ending in -viridae denotes a viral | family |
| List and describe the main steps of animal virus replication | adsorption penetration uncoding synthesis assembly release |
| What is the difference between DNA virus replication and RNA virus replication? | RNA is in cytoplasm and DNA has to be transcribed |
| Viruses that infect animal cells can never infect human cells | False |
| Describe the main difference between the lytic and lysogenic phase of viral replication | Lytic destroys cell Lysogenic stays dormant and can be turned on to the lytic stage |
| The term plaques is only used to describe the effects of bacteriophage on cell cultures | False-all viruses produce plaques |
| What is a prion? | -common feature of spongiform encephalopathies -distinct protein fibrils deposited in brain tissue of affected animals |
| ____________ is disinfection on a living surface | antisepsis |
| Which should be more "harsh" or work better: antisepsis or sanitization? | antisepsis |
| order of most resistant to least resistant | endospores mycobacteria protozoan cysts fungal spores gram + bacteria enveloped viruses |
| Describe the difference between a bactericidal agent and a bacteriostatic agent | bactericidal means killing of bacteria bacteriostatic means limiting the growth of bacteria |
| List and describe four factors that affect microbial death rate | number of bacteria population type of microbial growth temp and pH |
| What are the four cellular targets of physical and chemical agents | cell wall cell membrane cellular processes proteins |
| Lower temperatures can be used with dry heat than moist heat | False |
| The lowest temp required to kill all of the microbes in a sample in 10 minutes is the _________________ | thermal death point |
| Cold merely retards the growth of most microbes. | True |
| Filtration is not a method of sterilization. | False |
| Ultraviolet radiation produces _______ dimers that affect growth by causing ________ | pyrimidine absorption |
| Osmotic pressure achieves sterilization. T/F | False |
| Describe 4 desirable qualities of a germicide. | -rapid action in low concentration -solubility in water or alcohol and long term stability -penetration of inanimate surfaces to sustain a cumulative or persistent action -broad spectrum microbial action without toxicity to human and animal tissues |
| Describe 3 factors that affect the actions of a germicide | number of microbes how contaminated is it time of exposure |
| The most extensively used of all chlorine compounds is _________ | Bleach |
| Phenol is still extensively used as a disinfectant | False |
| A higher concentration of alcohol is more effective than a lower concentration | True |
| List 2 acids used in food preservation | lactic acid ascorbic acid |
| Describe 4 characteristics of an ideal antimicrobial drug | not toxic to the host microbicidal not resistant potent long enough to effectively work and not broken down |
| The _________ test shows antimicrobial susceptibility using large agar plates, a bacterial lawn, and antibiotic-infused discs. | Kirby Bauer |
| Each species of bacteria has the same susceptibility to a particular drug | False |
| Identification of the species of bacteria in an infection is necessary to accurately determine antibiotic susceptibility. | True |
| An antibiotic with a therapeutic index of 4 is less toxic than one with a therapeutic index of 40 | False |
| Microbial susceptibility is the only factor in choosing the right drug. | False |
| Describe some adverse reactions to antimicrobials. | allergic reaction diarrhea nausea/vomitting |
| The ____________ account for the greatest number of drug allergies. | Penicillin |
| Overgrowth of certain microbes due to antibiotic therapy that cause infection is known as __________. | Superinfection |
| The type of drug that inhibits cell wall synthesis is a _________ drug. Describe how it works. | Beta-Latam inhibition of cell wall synthesis and target the penicillin binding proteins |
| An antibiotic that acts on the bacterial cell wall will have little effect on a human cell. | True |
| Describe some ways that protein synthesis inhibitors might work | -incorrect amino acid insertion -block movement of RNA -attack one or both subcomponents of the 70s, 50s, or 30s ribosomes |
| An antibiotic that acts on the bacterial ribosome will have no effect on a human cell. | False |
| The least selectively toxic antibiotics are | ones that target the cell wall and folic acid synthesis |
| Antifungal and antihelminthic drugs can be toxic to human cells | True |
| What are some targets of antifungal? | membrane function tubal formation |
| Generally, how do anti-protozoan and anti-helminth drugs work? | inhibit function of the microtubules |
| There are as many antiviral drugs as there are antibiotics? | False |
| What are three ways can we target viruses? | barring penetration blocking transcription preventing maturation |
| What are some ways we can selectively target HIV replication? | reverse transcriptase |
| Bacteria can be resistant to antibiotics without ever encountering the drug | True |
| List and describe the 5 mechanisms of antibiotic resistance | -new enzymes are synthesized -permeability or uptake of the drug into a bacterium is decreased -drug is immediately eliminated -binding sites for drug are decreased in number -an affected metabolic pathway is shut down |
| What are the current drugs of last resort? | |
| What is a superbug? | a strain of bacteria that has become resistant to antibiotic drugs |
| Many antibiotics prescribed to humans are for viral infections . | True |
| Nearly 80% of all antibiotics in the U.S. are given to ____________ | livestock |
| ___________ are a novel treatment that have been used to target specific bacteria and effectively treat bacterial infections. | Phages |
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