Microbiology exam 3

What determines lysis or lysogeny?

- repressor proteins - environment

What are the 5 phases of viral replication?

1. Attachment- of the virion to host cell 2. Penetration- of the virion nucleic acid into the host 3. Synthesis- of virus nucleic acid and protein by host cell machinery as redirected by the virus 4 assembly- of the capsids and packaging of viral genomes into new visions 5. Release- of new virions form the cell

What are the three possible fates of transferred DNA?

1. Degraded by restriction enzymes. 2. Replicate itself 3. Recombine with host chromosome

what are the two modes of transduction?

1. generalized transduction 2. specialized transduction

what results from Hfr formation?

1. synthesize F pilus 2. mobilize DNA for transfer to another cell 3. alteration of surface receptors and cell no longer recipient

what are the three major phases of regulation of differentiation involving bacteria sporulation?

1. triggering the response 2. development of differentiated cells 3. reciprocal communication

What is a mutagen?

A chemical, physical or biological agent that increases mutation rates

What is a missense mutation?

A mutation in which a single codon is altered so that one amino acid in a protein is replaced with a different amino acid

What is a silent mutation?

A mutation that doesn't affect the phenotype of the cell

What is a transition mutation?

A purine replaced by a purine or a pyrimidine replaced by a pyrimidine

What is a transverse mutation?

A purine replaced by a pyrimidine or vice versa

What is a temperate virus?

A virus whose genome is able to replicate along with that of its host without causing cell death is a state called lysogeny

What test is used to detect revertants in large populations of mutant bacteria to show the potentially hazardous chemical?

Ames test

What is a mutant with a nutritional requirement for growth called and what is its parent called?

Auxotroph; prototroph

What is the number of virions released called?

Burst size

What is the protein shell that contains the virus genome called?

Capsid

What does the Ames test also test for?

Carcinogens

What is a nucleotide base analog?

Chemical mutagen molecules that resemble purines and pyrimidines bases of DNA that result in faulty base pairing

What is it called when several genomic units are recombined end to end to form a long DNA molecule?

Concatemer

What is the way in which DNA transfer requires cell-to-cell contact and a conjugation plasmid in the donor cell called?

Conjugation

What does the Nif regulon do?

Coordinates regulation of 20 genes essential to nitrogen fixing

What damage does ionizing radiation do?

Damages macromolecules in cells and causes DNA strands to break, rearrange or delete components

What is the role of a swarmer cell in caulobacter differentiation?

Dispersal as swarmer cells can't divide or replicate DNA

What are early proteins?

Enzymes for DNA replication , modification host polymerase (sigma factors); they recognize only phage promoter

What type of linkage do archaea have between lipids?

Ether linked

Why are eukaryotic mutation rates 10x slower than prokaryotes?

Eukaryotes have larger genomes; less proof reading in RNA than DNA

What is screening?

Examining large numbers of colonies looking for differences

What is a virion?

Extra cellular form that allows the virus to travel from one host cell to another( viruses cant replicate unless virion has entered the host)

What is heterocyst formation?

Formation of filamentous cyanobacteria that requires numerous morphological and metabolic changes

What is a virus?

Genetic element that cannot replicate independently of living host cell; intracellular parasite

What are selectable mutations?

Give mutant growth advantages under certain conditions example antibiotic resistance

What is rod-shaped viruses such as TMV called?

Helical symmetry

What is a double stranded DNA composed of single strands from two different sources?

Heteroduplex regions.

What is an example of an auxotroph?

His-

What is the most efficient arrangement of subunits to enclose a space which is 20 triangular faces?

Icosahedral symmetry

What damage does nonionizing radiation do?

Impedes DNA polymerase or causes misread

What are mutations due to agents in the environment called?

Induced mutations ( ex. Radiation from sun)

What mutagen causes frameshift mutations?

Intercalating agents

What is the latent period?

It is composed of the eclipse and maturation phases where viruses are being assembled inside the host cell; latent period ends when the host cell is lysed

What is the purpose of RNA replicases for viruses?

It replicates the viral RNA genome because viruses can't make RNA from an RNA template

What may also be altered in a mutant beside the genotype?

It's phenotype

What is an example of a temperate phage?

Lambda or P1

What are some examples of repressors?

Lambda repressor or Cro

What are the two proteins involved in SOS repair systems?

LexA and RecA

Most virus's genomes are what shape?

Linear

What is a cell that harbors a temperate virus called?

Lysogen

What enzyme carried by viruses is used to make holes in cell walls and lysis bacteria?

Lysozyme

What is a strain of any cell or virus carrying a change in nucleotide sequence?

Mutant

What is an inheritable change in the base sequence of the genome of an organism called?

Mutation

What are point mutations?

Mutations that occur only in one base pair ( caused by base pair substitutions in DNA)

What are the two main categories of mutagenic electromagnetic radiation?

Nonionizing and ionizing

What is an example of nonionizing and ionizing radiation?

Nonionizing- UV Ionizing- x-rays

What is a mutation in which the codon for an amino acid is changed to a stop codon?

Nonsense mutation

What is a use of lysed cells?

Nutrients

What are two main effectors on N-fixing?

Oxygen Ammonia

What is recombination?

Physical exchange of DNA between genetic elements

What are clear zones that develop on host cell lawns?

Plaques

What is the largest lineage or phylum of bacteria?

Proteobacteria

what are conjugation plasmids that carry antibiotic resistance genes called?

R factors

What is the key to homologous recombination?

RecA

What are specific host cell surface components the help in attachment?

Receptors

What is a wild-type strain?

Refers to a strain isolated from nature

What are promoters?

Regions upstream of a structural gene where RNA polymerase binds to initiate transcription

What method is used for screening large numbers of colonies?

Replica plating

What is the role of a stalk cell in caulobacter differentiation?

Reproduction and holdfast

What do retroviruses in animals need in order to make DNA from RNA?

Reverse transcriptase

What is it called when a mutation reverses effects of prior mutation and restores original phenotype?

Reversion or back mutation

What is circular permutation and what bacteriophage uses this?

Same set of genes arranged in different order; T4 phage

Levels of this sporulation factor determines if a spore is produced.

Spo0A

What are mutations that occur without external intervention called?

Spontaneous mutations (ex. Result from errors in bases pairing from DNA polymerase)

What are mutations that compensate for the effect of the original mutation called?

Suppressor mutations

What structure allows virions to attach to the host?

Tail fibers

What structure is compared to a syringe in how it injects the viral DNA into the host?

Tail tube

What is repeats on each end of a genome called?

Terminally redundant

What do tail fibers interact with to attach the virus to the host?

The LPS

What is the nucleocapsid?

The inner structure of nucleic acid plus capsid protein in enveloped viruses

What is homologous recombination?

The process that results in genetic exchange between homologous DNA from two different sources

What is important in the attachment to the host cell?

The proteins of the virion

What is the strain in which the original phenotype is restored called?

The revertant

What is a prophage?

The state of the genome of a temperate virus when it is replicating in synchrony with the host genome

What happens in virulent infections?

The virus replicates and destroys the host cell

How can frame shift mutations be restored?

Through genetic recombination only

What is the number of infectious units per volume fluid called?

Titer

What is the way in which DNA transfer is mediated by a virus called?

Transduction

What is the way in which free DNA released from one cell is taken up by another cell called?

Transformation

What are the 3 mechanisms of gene exchange?

Transformation Transduction Conjugation

What is the study of viruses called?

Virology

What are the two events that can take place once a virus is inside the host cell?

Virulent infection or lysogenic infection

What is secondary fermentation?

When an organism obtains energy from fermentation products produced by other bacteria (lactic acid)

What is infection?

When the virus's virion entered the host cell

Plaque assays are often used to estimate the number of virions in a sample of a particular volume (the titer). The count is given as plaque-forming units. Which of the following is NOT generally a concern that must be considered in evaluating the results of plaque assays? a. The largest problem is that single viruses may create multiple plaques, resulting in overestimates of the number of viruses present. b. The plaques must be clearly visible in order to be counted accurately; this technique cannot be used with viruses that do not cause clear cellular damage. c. The plaques must be at a density that can be counted on the plate; high and low densities may result in inaccurate counts.

a

what is electroporation?

a physical technique that is used to get DNA into organisms that are difficult to transform

what is an episome?

a plasmid that can be integrated into the host chromosome ex. F plasmid

When describing the bacteriophage genome, which terms could be used? a. ds DNA b. ss RNA c. ds RNA d. ss DNA

all of the answers are correct

Bacteriophage have a ________ complex structure than animal viruses, because ________. a. less / there prokaryotic cells have a simple structure compared to eukaryotic cells b. more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cells c. more / the bacteriophage must penetrate the peptidoglycan cell wall d. less / the bacteriophage does not have to penetrate the nucleus

c.

Restriction is a. a general host mechanism to prevent virus particles from further infective action. b. the viral process whereby a host's DNA ceases normal functioning. c. a general host mechanism to prevent the invasion of foreign nucleic acid. d. the viral process whereby the virus prevents other viruses from entering the cell.

c.

What are the caulobacter cell cycle regulatory proteins called?

ctrA GcrA DnaA

what is the alteration of the phenotype of a host cell by lysogenization called?

phage conversion

what is the mechanism of DNA transfer during conjugation?

rolling circle replication

what are segements of DNA that move as a unit from one location to another within DNA molecules?

transposable elements