Microbiology 261 Exam 2 Study Guide

What is a bacteriophage?

A virus that infects bacteria.

T/F : In both cocci as well as rod-shaped cells, new peptidoglycan synthesis occurs in both directions from the central location of the FtsZ ring.

False

T/F : In catabolic repression, cells always use the least abundant carbon source first.

False

T/F : In order to replicate its genome, a positive-strand RNA virus must produce a complete negative-strand RNA molecule that serves as the template for protein synthesis.

False

T/F : In prokaryotes, DNA viruses replicate their genomes in the nucleus while RNA viruses are replicated in the cytoplasm.

False

T/F : Lysogeny is unique to bacteriophages; similar relationships have not been found among the animal viruses.

False

T/F : Natural antibiotics are produced by all bacterial genera.

False

T/F : Penetration requires that the entire virus is inserted within the host.

False

T/F : Persistence is a heritable trait.

False

T/F : Rod-shaped viruses have icosahedral symmetry while spherical viruses have helical symmetry.

False

T/F : The Baltimore classification scheme is a useful way to categorize viruses based on their host infectivity.

False

T/F : The lacZ gene is commonly used as a reporter gene, because its substrate lactose is well known and easily measured.

False

T/F : The latent phase in the viral growth curve and the lag phase of the bacterial growth curve are equivalent and represent the time it takes for the virus or bacterium to adapt to the culture conditions and begin growing.

False

T/F : The origins of the nucleic acid polymerases used by viruses are eukaryotic.

False

T/F : The spherical shape of Staphylococcus aureus is a result of MreB function.

False

T/F : Viruses are known to infect Bacteria, but no virus has yet been found that infects Archaea.

False

T/F : Viruses do not contain their own nucleic acid polymerases.

False

T/F : When environmental levels of amino acids become limited, synthesis of mRNA, rRNA, and tRNA increases immediately.

False

Viroids infect only fungi.

False

When a solution composed of bacteria and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.

plaques

Based on its function, which type(s) of viruses likely contain(s) a gene encoding for RNA replicase?

positive and negative ssRNA viruses

Which type of viruses can be directly used for translation?

positive ssRNA

Regulation of enzyme activity occurs

posttranslationally.

On what basis can prions be differentiated from all other infectious agents?

prions are infectious proteins whose extracellular form contains no nucleic acid

What is the advantage of using genetic engineering to make insulin?

produce large amounts of useful substances; clean reproduction

Viruses infecting ________ are typically the easiest to grow in the laboratory.

prokaryotes

What is rBST used for?

rBST is injected into cows so they produce more milk

In order for the helix-turn-helix motif to bind to DNA, the ________ must fit into the major groove of the DNA.

recognition helix

The CRISPR system

recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.

Explain how you could clone a gene for insulin production into E. coli.

recombinant DNA introduced into suitable host for replication; yields mixture of recombinant constructs in which only some cells contain the desired gene

Hfr means high frequency of ________, and these cells are capable of transferring genes from their ________ to other cells.

recombination / chromosome

Regulatory proteins

regulate transcription, bind specific DNA sites, and can be influenced by small molecules.

When more than one operon is under the control of a single regulatory protein, the operons are collectively called a

regulon.

A plasmid may

replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.

A(n) ________ gene is a gene that encodes a protein that is easy to detect and assay.

reporter

The genes encoding green fluorescent protein (GFP) and β-galactosidase are typically used in cloning as

reporter genes.

What keeps temperate phages latent?

repressor proteins cI protein (lambda repressor): causes repression of lambda lytic events Cro repressor: controls activation of lytic events

Which type of regulators specifically bind to operator regions of DNA?

repressors

What is EcoRI? What is it used for?

restriction endonucleases/enzyme that in molecular biology it is used as a restriction enzyme that produces sticky ends

What type of virus is HIV? What does it cause?

retrovirus (RNA virus) AIDS

A drug designed to inhibit reverse transcriptase activity would target

retroviruses.

What are kinases and what is their role in two-component regulatory systems?

sensor kinase—detects environmental signal and autophosphorylates; found in cytoplasmic membrane response regulator kinase—DNA-binding protein that regulates transcription; found in cytoplasm

Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?

silent mutation

What is antigenic shift?

the process by which two or more different strains of a virus, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains; major change in influenza virus antigen due to gene reassortment pandemic (worldwide outbreaks) associated with Influenza

The promoters of positively controlled operons require activator proteins because

the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

A point mutation refers to mutations involving

a substitution, deletion, or addition of one base-pair.

How does a prion differ from a viroid?

a viroid is an RNA with no protein a prion is protein with no nucleic acid

How does a prion differ from a virus?

a virus contains both nucleic acid and protein a prion is protein with no nucleic acid

Regarding the viral membrane of an enveloped virus, the lipids are derived from the ________, and the proteins are encoded by ________.

hosts cell membrane / viral genes

When a virus enters a host cell in which it can replicate, the process is called an

infection.

Viral replication occurs

intracellularly.

Enveloped viral membranes are generally ________ with associated virus-specific ________.

lipid bilayers / proteins

The T4 bacteriophage could not infect Staphylococcus aureus because this bacterium does NOT possess a

lipopolysaccharide outer membrane.

What are the important differences among a recombinant live attenuated vaccine, a vector vaccine and a subunit vaccine?

live attenuated vaccine: Live attenuated vaccines contain a version of the living microbe that has been weakened in the lab so it can't cause disease. vector vaccine: Recombinant vector vaccines are experimental vaccines similar to DNA vaccines, but they use an attenuated virus or bacterium to introduce microbial DNA to cells of the body. subunit vaccine: Instead of the entire microbe, subunit vaccines include only the antigens that best stimulate the immune system.

Biofilm formation in Vibrio cholera is triggered by ________ cell densities and repressed by ________ cell densities.

low; high

Some bacteriophage possess an enzyme similar to ________, which makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.

lysozyme

A virus that kills its host is said to be

lytic or virulent.

Transcriptional regulators bind most frequently at the ________ site of DNA.

major groove

As a consequence of infection by a temperate bacteriophage such as lambda, the host cell

may lyse or may continue to divide and replicate both itself and the prophage.

What units are used to measure viruses?

nanometers (nm)

Viral size is generally measured in

nanometers.

The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur.

negative / inducer

What is the function of heterocysts in cyanobacteria such as Anabaena?

nitrogen fixation

Heterocysts are specialized cells that undergo

nitrogen fixation.

Retroviruses are medically important viruses because

they include some viruses that cause cancer and HIV.

Early and late viral proteins are classified according to their relative

time of synthesis following host infection.

The use of ________ is the easiest and most effective way of studying many animal and plant viruses.

tissue or cell culture

The concentration of infectious plaque forming units (pfu) per volume of fluid is known as the

titer.

The uptake of free DNA from the environment ________, while transfer of DNA with cell-to-cell contact would most likely result in ________.

transformation / conjugation

The HIV genome consists of

two identical ssRNA molecules.

The growth of viruses in a culture is described as a one-step growth curve, because

virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.

What is a naked virus?

virus without an envelope

Cells that have "insertional inactivation" of the lacZ gene are

white

Restriction is

a general host mechanism to prevent the invasion of foreign nucleic acid.

What is antigenic drift?

a mechanism for variation in viruses that involves the accumulation of mutations within the genes that code for antibody-binding sites epidemic (localized outbreaks) associated with Influenza

What do viroids infect?

plant cells only

The Ti plasmid is best suited for genetically manipulating

plants.

How does a transducing particle differ from an infectious bacteriophage?

1. A transducing particle is part of the host DNA that is packaged into a bacteriophage with lytic cycles and an infectious bacteriophage contains the vrial genome. 2. While the transducing particles are known to be "defective", the infectious bacteriophage is known to be "infective". 3. Transducing particles have low efficiency of bacterial transformations whereas the infectious bacteriopahges are highly efficient in the transformation process.

What are the four basic stages of biofilm formation?

1. attachment 2. colonization 3. development 4. dispersal

Describe how retroviruses reproduce.

1. retrovirus enters cell 2. virion envelope is removed at the host cell's membrane 3. reverse transcriptase transcribes one of the two RNA genomes 4. retroviral DNA is integrated into host genome 5. host cell transcribes retroviral DNA 6. retroviral RNA genome is assembled and packaged 7. enveloped virions are released from host cell via budding

The typical generation time of Escherichia coli is approximately ________ under optimal environmental conditions.

20 minutes

How do mutagens cause mutations?

A biological, chemical or physical agent that interacts with DNA and causes a mutation. nucleotide base analogs: resemble nucleotides but have faulty base-pairing due to a different side group incorrect base pairing, which can inhibit replication or cause mismatching

What is a transgenic plant?

A genetically engineered organism that contains a gene from another organism; Ti plasmid contains genes that mobilize DNA for transfer to plant; responsible for virulence T-DNA: plasmid segment transferred to plant; sequences at ends essential for transfer

How is a lytic virus different from a latent virus? What other terms are used to describe latent viruses?

A lytic virus lyses the host cell after infection, killing host. A latent (lysogenic or temperate) virus replicates their genome in tandem with host genome, without killing the host; can live in a stable genetic relationship within the host, but also can lyse the cells in a lytic phase.

What is an inducer?

A substance that induces enzyme synthesis.

T/F : A bacteriophage that lacks its proteinaceous capsid structure is also called a viroid.

False

Why do antibiotics that target bacterial ribosomes not make humans sick?

All of the antibiotics that target bacterial protein synthesis do so by interacting with the bacterial ribosome and inhibiting its function. Human cells do not make or need peptidoglycan. ... The result is a very fragile cell wall that bursts, killing the bacterium.

What is unique about the Pox viruses? What type of damage do they do to their host?

All replication occurs in the cytoplasm and they code for all the proteins needed for their replication Pox viruses cause the cell to lyse, killing host cell.

What is a host?

An organism that provides a source of energy for a virus or another organism

Why is the presence of a cell wall significant from a clinical standpoint?

Animal cells do not have cell walls, so antibiotics that target cell walls can selectively destroy invading microorganisms.

Why are efflux pumps capable of conferring multi-drug resistance?

Efflux pumps are ubiquitous and transport various molecules, including antibiotics, out of the cell.

T/F : A naked virus lacks a capsid.

False

What are some examples of mutagens?

Athetium Bromide (chemical)—stain used on DNA in gel then placed on UV light and bands fluoresce Nonionizing Radiation (ex. UV light)—pyrimidine dimer Ionizing Radiation (ex. X-rays, cosmic rays, and gamma rays)—ionize water, forming free radicals such as hydroxyl radical (OH·) that damage macromolecules, leading to double- or single-stranded breaks and rearrangements or large deletions, and causes breaks in DNA that leads to mutations

T/F : A phage can be infectious even if all of its DNA has been replaced by bacterial DNA.

False

What are autolysins and why are they necessary?

Autolysins break cell walls; creates small gaps for growing points by hydrolyzing bonds between N-acetylglucosamine and N-acetylmuramic acid; new cell wall material is added across gaps. Important in the formation of new cell walls during binary fission.

What is an auxotrophic mutant and how would you screen for it?

Auxotrophs have an additional nutritional requirement for growth. Screen for it by replica plating screens: 1. Transfer colonies from master plate 2. Inability of colony to grow on a medium lacking a nutrient indicates mutation (selective medium) 3. Colony on master plate is picked, purified, and characterized.

Some antibiotics target peptidoglycan synthesis. What is a molecular growth target of an antibiotic that inhibits peptidoglycan synthesis?

Bacitracin binds to bactoprenol and prevents new peptidoglycan precursors from reaching site of synthesis.

What is the divisome?

Cell division apparatus; formed by several essential proteins called Fts proteins interacting; forms about ¾ of the way into cell division; contains proteins for peptidoglycan synthesis and synthesis of new cytoplasmic membrane and new cell wall FtsZ: crucial to binary fission; found in almost all Archaea; attach around center of cell in a ring that becomes the cell-division plane ZipA: anchor that connects FtsZ ring to cytoplasmic membrane FtsA: related to actin; recruits other divisome proteins; helps connect FtsZ ring to membrane FtsI: penicillin-binding protein (inhibited by penicillin antibiotic)

What is the CRISPER system?

Clustered Regulatory Interspaced Short Palindromic Repeats - the prokaryotic "immune system" that evades viral destruction and maintains genome stability

What is meant by competence in genetic transformation experiments?

Competency—a cell that can take up DNA and be transformed; capability to do this is genetically determined; the state of being able to take up exogenous DNA from the environment

T/F : All viruses contain their own nucleic acid polymerases.

False

How are constitutive proteins different from inducible proteins?

Constitutive proteins are needed at the same level all the time in the cell. Inducible proteins are synthesized only when they are needed.

The packaging mechanism of T4 DNA involves cutting of DNA from

DNA concatemers.

T/F : An RNA genome itself serves as mRNA in negative-stranded RNA viruses.

False

The enzyme that covalently links both strands of a vector and inserted DNA in molecular cloning is

DNA ligase.

In the process of binary fission in Bacteria, which action occurs first?

DNA replication

What is an isoenzyme?

Different enzymes the catalyze the same reaction, but is subject to different regulatory controls.

T/F : Bacterial mating (or conjugation) is a bidirectional process where nucleic acids (DNA or RNA) are transferred between two cells.

False

What advantage do quorum-sensing systems confer on bacterial cells?

Ensures that a sufficient number of cells are present before initiating a response that, to be effective, requires a certain cell density. Prokaryotes can respond to the presence of other cells of the same species (assess population density).

T/F : Genetically modified plants resistant to the herbicide glyphosphate contain a gene from Bacillus thuringiensis.

False

Why does attenuation control not occur in eukaryotes?

Eukaryotic transcription and translation do not occur simultaneously as they do in prokaryotic gene expression.

When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs?

Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

Why do frameshift mutations generally have more serious consequences than missense mutations?

Frameshift mutations completely alter the entire protein sequence that occurs after the mutation (often a results in complete loss of protein function), whereas a missense mutation only alters a single amino acid.

Which of the following proteins is most active in divisome complexes?

FtsZ

Which reporter gene yields a green colored product?

Green Fluorescent Protein (GFP)

What would happen to regulation from a promoter under negative control if the region where the regulatory protein binds was deleted?

If the regulatory protein-binding region of a promoter under negative control were deleted, one would expect constitutive production of the operonal gene products. If, on the other hand, a positive control region were deleted, one would expect no production of the operonal transcript since there would be no place for the activator protein to bind.

What is Taq?

It is a DNA polymerase used in PCR because it can withstand high temps. DNA polymerase is the only enzyme used in cellular DNA replication that is required to preform PCR.

What is the function of bactoprenol?

It is a hydrophobic alcohol that transports peptidoglycan precursors across the cytoplasmic membrane.

How does attenuation work?

It is a transcriptional control that functions by premature termination of mRNA synthesis. Control is exerted after initiation of transcription, but before its completion. The mRNA step loop structure and the synthesis of the leader peptide are determining factors of attenuation.

What causes bacteria to fluoresce?

Lux operon encodes for luciferase, the enzyme that causes bioluminescence.

Describe at least two targets of antibiotics and discuss why the drugs are effective.

Many antibiotics target DNA replication, RNA synthesis, and translation. Quinolones target DNA gyrate and topoisomerase IV by interfering with DNA unwinding and replication. Rifampin and acitinomycin prevent RNA synthesis by blocking RNA polymerase active site or RNA elongation. Antibiotics can inhibit protein synthesis as well. Puromycin binds to A site in 70S, inducing chain termination and inhibition protein synthesis. Aminoglycoside antibiotics (streptomycin) target 16S rRNA of 30S ribosomes, leading to error-filled proteins.

How does FtsZ find the cell midpoint of a rod shaped cell?

Min proteins facilitate the localization of the cell's midpoint by FtsZ. The FtsZ proteins with other proteins known as Min proteins. The Min proteins are Min C, D, and E. MinD forms the spiral structure. It also helps MinC in protein localization. C and D can inhibit cell division by obstructing formation of the FtsZ ring. MinE pushes away C and D to the poles to allow the FtsZ ring to be formed.

The major shape-determining factor in Bacteria is the protein

MreB.

Distinguish between a mutation and a mutant.

Mutation—A heritable change in DNA sequence that can lead to a change in phenotype (indicated by 3 lowercase and 2 uppercase) Mutant—a cell or virus derived from a wild type that carries a nucleotide (genotype) sequence change (phenotypic change represented by a +/-)

What is the difference between the native and pathogenic forms of a prion protein?

Native prions live in the organism at all times and adapt to environmental conditions. Pathogenic prions cause native prions to change their shape (and henceforth their function) leading to amyloid plaques in brain.

What are the possible consequences of viral infection of an animal cell?

Outcomes vary from rapid lysis to persistent infections, latent infections, or cancer.

How does PCR work and when would you use it?

PCR(polymerase chain reaction) requires DNA polymerase (naturally copies DNA) and artificial oligonucleotide primers made of DNA; DNA replication in vitro, multiply segments of target DNA up to a billion fold during amplification (doubling) PCR can be used for cloning or sequencing, phylogenetic studies, amplifying very small DNA quantities, medical diagnostics, and forensic science.

When an animal cell gets infected with a virus what are the possible consequences?

Persistent infections: release of virions from host cell does not result in cell lysis, the infected cell remains alive and continues to produce viruses; may come out with fever Latent infections: when the virus enters the host chromosome and are known as proviruses and can go into lytic cycle. Delay between infection by the virus and lytic events.

How is the penetration step in viral replication different in phages and animal viruses? What else would be different in their replication?

Phages inject their nucleic acid into the bacteria and the capsid stays on the outside of the host. Many are naked. Animal viruses are taken completely into the host cell and must be uncoated to release the viral nucleic acid. Replication is also different because eukaryotic cells have a nucleus. Many bud out of the host so they are enveloped.

How is positive control different from negative control?

Positive control causes transcription and negative stops transcription.

Distinguish between a positive-strand RNA virus and a negative strand RNA virus.

Positive-strand RNA viruses are the same as mRNA and can be directly translated. Negative-strand RNA viruses are complementary to mRNA and must be copied before translated.

Contrast mRNA production in the two classes of single stranded RNA viruses.

Positive-strand RNA viruses are translated to viral proteins (RNA Polymerase, which copies the strand to make more viral DNA); positive copied into negative strand to provide a template for more positive strands. Negative-strand RNA viruses are copied to make a positive strand (template for more negative strands) by RNA Polymerase then translated into viral proteins.

An organism grown in nutrient rich broth to high turbidity always produces a blue pigment. When a large inoculum is transferred to a nutrient rich agar plate, it also appears blue. A researcher noticed that this never happens when very small colonies are grown on low nutrient agar plates, however. What is the most plausible conclusion?

Production of the blue pigment production is linked to quorum sensing.

How is provirus different from a prophage?

Provirus is in animal cells (in cytoplasm and nucleus). Prophage is in bacteria cells (only in cytoplasm).

The major symptoms of the genetic disorder cystic fibrosis are caused due to biofilm formation by

Pseudomonas aeruginosa.

Reverse transcriptase is a(n)

RNA-dependent DNA polymerase

Explain why recombinant vaccines might be safer than some vaccines produced by traditional methods.

Recombinant vaccines can modify a pathogen with genetic engineering to delete virulence factors and retain those that elicit immune responses; large amounts of immunogenic proteins can be administered at high dosage with less risk than attenuated or killed vaccines.

What are reporter genes and why are they useful?

Reporter genes encode proteins for an easy-to-detect assay and are fused to genes of interest, enabling visualization of proteins and monitoring gene expression.

What are reoviruses?

Respiratory Enteric Orphan virus - a group of dsRNA viruses that infect respiratory tract and intestines, not associated with a specific disease; generic unlike polio disease that cause polio

Where did Taq come from and why is that beneficial?

Taq came from the thermophilic bacterium Thermus aquaticus and is crucial in PCR because it can withstand high temperatures; adds template-independent adenosine to 3' end.

What is unique about retroviruses?

Retroviruses are RNA viruses that contain the enzyme reverse transcriptase. Reverse transcriptase copies the single stranded RNA into double stranded DNA which then integrates into the host chromosome and becomes a provirus. ex: HIV

What is unusual about genetic information flow in retroviruses?

Retroviruses use reverse transcriptase enzyme to turn ssRNA into dsDNA then go into a provirus stage.

What is the name of the virus that causes rabies?

Rhabdovirus

What disease is associated with coronaviruses?

SARS (Sudden Acute Respiratory Syndrome)

Name some prion diseases and the organisms they are found in.

Scrapie in sheep Bovine Spongiform Encephalopathy (BSE) in cows

Distinguish between screening and selection.

Selectable mutations—confer an advantage; mutant children can outgrow and replace parent under certain environmental conditions (Ex. antibiotic resistance) Screening mutations—do NOT confer an advantage even though a phenotypic change may occur; requires laborious, time-consuming screening (examining large numbers and looking for differences) to find (Ex. Color loss in a pigmented organism)

Name at least two common diseases caused by herpesviruses.

Simplex I—cold sores Simplex II—genital herpes Epstein Barr—mono HPV—genital warts, cervical cancer Varicella-zoster - chicken pox and shingles

What are the advantages of using super-resolution microscopy vs standard fluorescence microscopy?

Super-resolution microscopy has a resolution of 10-50nm in living cells; allows observations of dynamic behaviors in real time; and can resolve multiple proteins, different nucleic acids, and different loci within one nucleic acid molecule (when combined with fluorescent tagging).

How are T4 and Lambda similar and different?

T4 and Lambda are bacteriophages containing dsDNA, that infect E. coli T4—lytic Lambda—latent

How does MreB control the shape of a rod-shaped bacterium?

The MreB protein controls shape by forming microfilament like structures which maintains the shape of the bacteria. If MreB is inactivated, it causes cell to become cocci (default shape).

What is the difference between an allosteric site and an active site?

The active site is where a substrate binds in order for the enzyme to do its purpose. The allosteric site is where an inhibitor binds to change the conformation of the enzyme's active site so that substrates cannot bind and the enzyme cannot fulfill its purpose.

T/F : Proteins and RNA molecules that are needed in the cell at about the same level under all growth conditions, require constitutive expression.

True

T/F : Proteins required at approximately the same level throughout a cells growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.

True

T/F : Quorum sensing relies upon a large cell population which then turns on transcription.

True

T/F : RNA viruses contain their own nucleic acid polymerases.

True

T/F : Some proteins that bind to DNA block transcription, whereas other proteins activate transcription.

True

T/F : Temperate viruses can enter into either a lytic or lysogenic cycle.

True

T/F : The genome of a temperate phage can replicate along with the host genome during lysogeny.

True

T/F : The key steps in cloning a foreign gene into a vector, regardless of the application, involve isolating the insert fragment, ligating the insert into a vector, and transforming it into a host.

True

The general steps of the viral lifecycle are similar in most viruses. One major exception, however, is entry into the host cell. How does this step differ between an animal cell and E coli?

The entire virion is taken into an animal cell, but only the viral genome enters E coli.

How does the lac operon work and is it controlled positively or negatively?

The lac operon is only transcribed when glucose is absent and other sugar sources are needed. It is physically blocked by a repressor protein when lactose is not needed, but allolactose (inducer) binds to repressor protein's active site when lactose is needed. The inducer (allolactose) changes the repressor protein's shape and falls off of the operator and transcription of the lac operon can proceed. The repressor's role is inhibitory so the operon is under negative control.

T/F : The preferential use of glucose over other available carbon substrates for growth is mechanistically explained by catabolite repression.

True

T/F : The reason dogs do not get measles is because their cells lack the correct receptor sites for that virus.

True

What is rBST and how is it made?

The gene that expresses bST is inserted into a bacterium using the recombinant DNA technique.(1) This bacterium can then produce a hormone identical to bST, which is called rbST.

T/F : The stringent response is a mechanism used by bacteria that provides increased ability to survive in environments lacking nutrients.

True

T/F : Toxigenicity in Corynebacterium diphtheriae is due to phage conversion.

True

In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription?

The inducer prevents the repressor from binding to the operator.

What role does cyclic AMP (cAMP) play in glucose regulation?

The level of cAMP concentration determines whether CRP can bind to the operon in order for it to be transcribed.

Explain how catabolite repression depends on an activator protein.

The repressed gene needs an activator protein to bind to it when glucose levels are low so that the lac operon can become active and lactose can be used as an energy source.

What do repressor proteins bind to?

The repressor protein binds to the operator region of a gene to block or repress transcription.

What are viral envelopes made of?

The viral envelopes are made of lipid bilayer with embedded proteins (spikes). They come from the host cell's cytoplasmic membrane (budding).

You isolate a bacteriophage that can replicate in E. coli. Through chemical analyses you determine that the only nucleic acid present is RNA. You isolate the RNA and put it in a test tube with all of the enzymes, amino acids, and RNAs necessary for translation. The RNA is translated directly, without being copied into a complementary strand first, and new infectious virions are made and released. What does this tell you about the bacteriophage?

The viral genome is ssRNA of the plus sense.

T/F : Viruses can confer additional properties on their host cells, which can in turn be inherited.

True

How do bacteria control what proteins are being expressed?

They synthesize genes that encode the proteins that are needed by the cell.

What is transpeptidation and why is it important to both the cell and clinical medicine?

Transpeptidation is the formation of peptide cross-links between the muramic acid residues in adjacent glycan chains. Its the last step in cell wall synthesis; its important because the cross linking of residues in peptido makes the cell wall intact.

T/F : A common reporter protein is green fluorescent protein (GFP).

True

T/F : A common structure for proteins that bind DNA is helix-turn-helix.

True

T/F : A lytic infection results in death of the host cell.

True

T/F : A two-component regulatory system usually involves both the sensor and response proteins being subject to phosphorylation.

True

T/F : All Hfr strains possess an F factor integrated into the host chromosome.

True

T/F : Almost all plasmids are double-stranded DNA.

True

T/F : An effective way to introduce DNA into plant cells is using the Ti plasmid, which comes from a plant pathogen.

True

T/F : Antibiotic resistance can develop in a bacterium as a result of spontaneous mutation.

True

T/F : Antibiotic-sensitive bacteria sometimes produce cells that are transiently resistant to multiple antibiotics.

True

T/F : Budding of virions from an infected host results in enveloped virus.

True

T/F : DNA polymerases from Escherichia coli cannot be used to artificially copy gene sequences with a thermocycler.

True

T/F : Modification enzymes typically methylate specific bases within the recognition sequence to prevent digestion of the nucleotide sequence by restriction endonucleases.

True

T/F : Most plasmids are circular rather than linear.

True

Describe a complex virus and give an example.

Virions are composed of several parts, each with separate shapes and symmetries. Example: bacteriophage

What types and arrangements of nucleic acids are found in viruses?

Viruses either DNA or RNA (single- or double-stranded) and may be circular or linear (mostly linear).

Compare and contrast conjugation and Hfr conjugation.

When F plasmids become integrated into a host chromosome they become Hfr (high frequency of recombination) i. Pili are used for conjugation; DNA transfer begins in the middle of F factor in host chromosome and normally breaks before completion, so the recipient is still an F- cell; the F genes that are in the recipient integrate into the host chromosome (host chromosome DNA is also transferred) Nonintegrated F plasmids used in regular conjugation are called F+ i. Pili are used for conjugation; single stranded copy of the F+ plasmid is transferred, each cell synthesized a complementary strand and contains a full F plasmid

What is catabolic repression?

While the cell is using glucose it does not need to express the genes for the metabolism of any other sugar (represses ALL operons except the one to breakdown glucose). Ensures that the organism uses the best carbon and energy source (glucose) first. An example of a global control system because many different genes are regulated at the same time.

How can a virus cause cancer?

When the viral DNA incorporates into the host chromosome it can also cause a mutation that results in a transformation of the host cell into a tumor or cancer cell. Normal cells have contact inhibition in which they grow to a certain density and then stop. Tumor cells lack contact inhibition and thus continue to reproduce and make tumors.

Which of the following are the hosts for most enveloped viruses? a. animals b. Archaea c. fungi d. Bacteria

a. animals

Which of the following enzymes would you expect to find in the virion of a retrovirus, but NOT in a bacteriophage? a. reverse transcriptase b. lysozyme c. methylase d. restriction enzymes

a. reverse transcriptase

Compare and contrast the activities of an activator protein and a repressor protein.

activator protein: binds to activator binding site and induces transcription repressor protein: binds to operator and represses transcription

Which of the following molecules functions as an intracellular signaling molecule during quorum sensing?

acylated homoserine lactones

Where in the body do you fine adenoviruses?

adenoids

What is the inducer for the lac operon?

allolactose

A prophage replicates

along with its host while the lytic genes are not expressed.

What is the host cell for hepadnaviruses?

animal liver cells

When two different influenza viruses infect the same cell, their segmented genomes can undergo reassortment which will result in

antigenic shift.

All viral particles

are metabolically inert.

For bacteriophages and animal viruses ________ is the step in the viral life cycle that determines host cell specificity.

attachment

There are four basic stages to biofilm formation. What is the correct order of these stages?

attachment, colonization, development, dispersal

A mutant that has a nutritional requirement for growth is an example of an

auxotroph.

Which of the following is most similar to lysogeny? a. F+ state b. Hfr state c. F- state d. F state

b. Hfr state

Quorum sensing generally follows the mechanism of which type of regulation? a. feedback inhibition b. a two-component regulation system c. positive transcriptional regulation d. negative transcriptional regulation

b. a two-component regulation system

All of the following can act as receptors for various bacteriophages EXCEPT a. iron transport proteins. b. cilia. c. sugar transporters. d. flagella.

b. cilia.

All of the following are TRUE statements concerning binary fission of microbial cells EXCEPT: a. a septum is formed across the midline of the cell. b. daughter cells produced can be of different sizes. c. the chromosome of the cell is replicated. d. elongation of the cell occurs and the chromosomes are pushed apart.

b. daughter cells produced can be of different sizes.

The term phage is generally reserved for the viruses that infect

bacteria.

Endospore formation is stimulated when

bacterial growth ceases due to limitation of an essential nutrient.

When DNA is transferred into a prokaryotic cell it may

be degraded by enzymes, replicate independent of the host chromosome, or recombine with the host chromosome.

After digesting a DNA sequence, a restriction endonuclease can generate

blunt ends, overhangs, or sticky ends.

What is the shape and type of the virus that causes rabies?

bullet shaped, enveloped, helical nucleocapsid containing several enzymes RNA virus

Mechanisms for controlling enzyme activity include all of the following EXCEPT a. degradation of the enzyme. b. feedback inhibition. c. addition of short sections of new amino acid sequence. d. covalent modification of the enzyme.

c. addition of short sections of new amino acid sequence.

All of the following are targets of currently used antibiotics EXCEPT: a. DNA synthesis. b. transcription. c. biofilm formation. d. translation.

c. biofilm formation.

Herpes viruses can cause all of the following diseases in humans EXCEPT: a. cancer. b. cold sores. c. spongiform encephalopathy. d. chicken pox.

c. spongiform encephalopathy.

What are capsids made of?

capsomeres

A bacterium that lacks the mreB gene will have a ________ shape.

coccoid

A concatemer is a

combination of two or more repeated nucleotide sequences covalently linked together.

Cellular receptors may be composed of

combinations of proteins, carbohydrates, and/or lipids.

Which of the following sequences is a palindrome, characteristic of many recognition sequences for restriction endonucleases? Which of the following sequences is a palindrome, characteristic of many recognition sequences for restriction endonucleases? a. GTAATG CATTAC b. TTGCCGA AACGGCT c. GGGGGGG CCCCCCCC d. GAATTC CTTAAG

d. GAATTC CTTAAG

Which of the following do NOT bind to the promoter sequence during regulation? a. inducers b. repressors c. activators d. None of these bind directly to the promoter sequence.

d. None of these bind directly to the promoter sequence.

In the bacterial world, a gene located on which of the following would be the LEAST likely to be transferred? a. the phage Mu b. an F plasmid c. a resistance plasmid d. the chromosome

d. the chromosome

Which of the following methods may introduce foreign DNA into a recipient? a. transduction b. conjugation c. transformation d. transformation, transduction, and conjugation

d. transformation, transduction, and conjugation

Bacteriophages genomes are typically composed of

double-stranded DNA.

For a virus to cause a latent infection, it must possess

dsDNA.

Prokaryotic restriction endonucleases are effective at destroying a virus whose genome consists of

dsDNA.

At which time period during PCR thermocycling is the hottest in temperature?

during DNA denaturation

The killing of cells by UV irradiation involves

formation of pyrimidine dimers

Genetic recombination involving insertion sequences typically results in what type of mutation?

frameshift mutation

Ionizing radiation includes

gamma rays, cosmic rays, and X-rays (NOT UV rays)

What is the difference between generalized and specialized transduction?

generalized—DNA from any portion of the host genome is packaged inside the virion (lytic phage) specialized—DNA from a specific region of the host chromosome is integrated directly into the virus genome (latent phage)

The size and shape of viral particles is largely governed by the size and packaging of the viral

genome.

The T4 phage protects its DNA from host restriction endonucleases by

glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.

What is a diauxic growth curve?

has two exponential growth phases if two energy sources are available

Hfr strains of Escherichia coli

have an integrated F factor.

Biofilm formation in Pseudomonas aeruginosa is triggered by ________ cell densities and repressed by ________ cell densities.

high; low

The process in which related DNA sequences from two different sources are exchanged is called

homologous recombination.

What are the basic components of a virus?

nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases

When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus

nucleocapsid.

The mutagens 2-aminopurine and 5-bromouracil are examples of

nucleotide base analogs.

Pseudomonas aeruginosa is a(n) ________ pathogen.

opportunistic

Why is pUC19 a great cloning vector?

pUC19 (a plasmid) carries a 54 base-pair multiple cloning site polylinker that contains unique sites for 13 different hexanucleotide-specific restriction endonucleases; vector and foreign DNA cut with the enzyme.

A cell that allows the complete replication cycle of a virus to take place is said to be a

permissive host.

The designations Phe-, Leu-, and Ser+ refer to an organisms

phenotype.

What are phosphatases and what is their role in two-component regulatory systems?

phosphatases remove phosphate groups from molecules In two-component regulatory systems, phosphatase removes the phosphate from the response regulator.

The function of a kinase is

phosphorylation

The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA.

pili

In conjugation, how are donor and recipient cells brought into contact with each other?

pilus

Why would cells want to control what protein is expressed?

specific proteins are synthesized to preform particular functions within certain conditions; additionally, this saves energy

What is feedback inhibition?

the end product of a metabolic pathway shuts down the pathway