Exam 3 Homeworks

In response to an external signal the response regulator of a two-component signal transduction system:

 

phosphorylates the promoter of an operon.

 

is phosphorylated and then interacts with the promoter of an operon.

 

phosphorylates (adds a phosphate to) itself and then phosphorylates a response regulator.

 

phosphorylates a response regulator.

is phosphorylated and then interacts with the promoter of an operon

A viral genome consists of

\
DNA

\
Both RNA and DNA

\
RNA

\
Either RNA or DNA

either RNA or DNA

Compared with cellular genomes, viral genomes: 

  

also must have double-stranded DNA as their genome.

 

are larger, with more base pairs.

  

have genomes composed of RNA only.

\
are smaller, with fewer base pairs

are smaller, with fewer base pairs

Expression of the operon below leads to an mRNA that encodes three proteins. This mRNA is described as being:

\
polycistronic

  

dicistronic

  

monocistronic

  

multicistronic

polycistronic

A temperate bacteriophage:

  

replicates in its host cells and then lyses the host cell to release new virions.

 

None of these answers are correct.

 

inserts its genome into the host cell's chromosome.

  

can either replicate and lyse its host cell to release new virions or insert its genome into the host cell's chromosome, depending on the nutrition of the host cell

can either replicate and lyse its host cell to release new virions or insert its genome into the host cell's chromosome, depending on the nutrition of the host cell

Some bacteria protect themselves from bacteriophage infection by utilizing Restriction-Modification systems.  These systems are composed of enzymes that:

  

modify bacterial cell ribosomes preventing bacteriophage mRNA from being translated.

 

modify bacterial cell RNA polymerase preventing transcription of the bacteriophage genome.

 

modify chromosomal DNA and cut bacteriophage DNA.

 

modify bacterial cell wall preventing bacteriophage from injecting their genome.

modify chromosomal DNA and cut bacteriophage DNA

True or False: Release of an animal virus from a host cell always requires lysis of the host cell.

  

True

 

False

false

Dr. Strummer is investigating a new strain *Escherichia coli* that is unable to maintain osmotic homeostasis in response to an increase in environmental salt concentrations.  DNA sequencing of this new strain reveals a mutation in the *envZ* gene that results in a non-functional EnvZ protein.  This strain is unable to respond to changing salt concentrations because:

  

it lacks the ability to directly activate the expression of the ompF gene.

 

it lacks the ability to sense the change in extracellular salt concentrations.

  

it lacks the ability to directly repress the expression of the ompC gene.

 

it lacks the direct positive regulator of the *ctxAB* genes

it lacks the ability to sense the change in extracellular salt concentrations

Consider a mutation in which the change is from the codon UCU which encodes serine, to ACU which encodes threonine. Which type of point mutation is this?

  

frameshift mutation

  

silent mutation

  

nonsense mutation

 

missense mutation

missence mutation

For any virus, what is the first step for causing infection?

  

Uncoating

  

Attachment

  

Release

 

Replication

attachment

Viral envelopes are composed of ________ that are synthesized by ________.

\
proteins, viral ribosomes

\
proteins, host ribsomes

\
phospholipids, host proteins

\
phospholipids, viral proteins

phospholipids, host proteins

Which of the following describes a change in an organism’s genotype (rather than its phenotype)? \n

Loss of polar flagella by *Vibrio cholerae* during colonization of its host.

  

Acquisition by *Corynebacterium* of a prophage that encodes diphtheria toxin.

  

Initiation of endospore formation by *Bacillus subtilis* during nutrient limitation.

  

Lack of red pigmentation by *Serratia marcescens* colonies on nutrient agar.

acquisition by *Corynebacterium* of a prophage that encodes diphtheria toxin

Wild-type cells of *Escherichia coli* can synthesize tryptophan, an essential amino acid. To do so, they need to express the five genes of the *trpEDCBA* operon (*trpE, trpD, trpC, trpB, trpA*) which encode enzymes that allow for the synthesis of tryptophan from chorismate. These genes are expressed at high level only when tryptophan is at low concentrations in the cell. When tryptophan concentrations in the cell are high, expression of the *trpEDCBA* operon is greatly reduced.

Deletion of a gene called *trpR* in a different region on the chromosome causes the *trpEDCBA* operon to be expressed at high level when cells are growing in a medium that has high concentrations of tryptophan.

What is the function for the product of the *trpR* gene in regulation of the *trpEDCBA* operon?

  

A negative regulator of the trpEDCBA operon.

  

A positive regulator of the trpEDCBA operon.

  

Both a positive and a negative regulator of the trpEDCBA operon.

 

Sigma factor required expression the trpEDCBA operon.

a negative regulator of the trpEDCBA operon

Viruses with an RNA genome are dependent on the host polymerase to copy its chromosome

  

True

 

False

false

*lacO* is:

  

A gene that codes for a protein that both positively and negatively regulates the expression of the arabinose operon.

  

A sequence of DNA in the lactose operon promoter.

  

A protein that negatively regulates the expression of the lactose operon.

 

A gene coding for a protein that negatively regulates the expression of the arabinose operon.

a sequence of DNA in the lactose operon promoter

When exposed to high heat, wild-type cells of *Escherichia coli*, will express the genes of the heat shock response. To do so, they need to transcribe multiple operons in the chromosome that encode for chaperone proteins and enzymes. These genes are expressed at high level only when *Escherichia coli* is at of temperature of 42oC or higher.

Deletion of a gene called *rpoH* on the *Escherichia coli* chromosome causes the genes of the heat shock response to be **NOT** expressed even when cells are growing at a temperature of 42oC or higher.  What is the role of the *rpoH* gene product?

  

A Sigma factor required for heat shock gene expression.

  

A negative regulator of heat shock gene expression. 

  

A positive regulator of heat shock gene expression.

  

It is impossible to tell with the information given

a Sigma factor required for heat shock gene expression

Quorum Sensing is:

  

the regulation of gene expression through the use of DNA rearrangements.

 

the regulation of gene expression through the use of alternative sigma factors.

  

the regulation of gene expression in response to fluctuations in cell-population density.

  

the regulation of gene expression in response to the concentration of a nutrient

the regulation of gene expression in response to fluctuations in cell-population density

In a bacterial chromosome, a grouping of adjacent genes organized under the control of a single promoter are referred to as:

  

a regulon

  

an operon 

  

an intron

  

a megatron

an operon

Dr. Strummer is working with a laboratory strain of *E. coli* that has a deletion mutation in the *lacO.*  Which of the following statements about this strain is correct:

  

This strain is lactose intolerant.

   

This strain will express the lactose operon when cultured in medium with low concentrations of glucose and lactose.

  

This strain will express the lactose operon when cultured in low glucose and expression is not dependent on the concentration of lactose in the culture medium

  

This strain will express the lactose operon when cultured in medium with high concentrations of glucose and lactose.

This strain will express the lactose operon when cultured in low glucose and expression is not dependent on the concentration of lactose in the culture medium

In response to ______ glucose conditions, adenylate cyclase synthesizes _______, which plays a role transcriptional regulation of *lac* operon.

  

low, cyclic AMP

 

high, ppGpp

  

low, ADP

  

high, AMP

low, cyclic AMP

The uptake of DNA released from a cell is ________, while transfer of DNA with cell-to-cell contact is referred to as________.

  

conjugation, transformation

 

transformation, conjugation

  

transformation, transduction

  

transduction, conjugation

transformation, conjugation

____________ is the evolution theory that mitochondria and chloroplasts arose from a symbiotic association of prokaryotes within another type of cell.

  

Exosymbiont Theory

 

Nucleus First Theory

  

Endosymbiont Theory

  

Mitochondrion First Theory

endosymbiont theory

Homologous recombination requires that the two recombining molecules have a considerable stretch of homologous DNA sequence.

\
True

  

False

true

Which of the following DNA repair mechanisms is error prone? \n

  

Light Repair

  

SOS Repair

   

Excision Repair

  

Mismatch Repair

SOS repair

Homologous recombination requires that the two recombining molecules have a considerable stretch of homologous DNA sequence.

  

True

 

False

true

Dr. Strummer is working with *Escherichia coli* 0AT-M1LK, a *lacZ***-**strain that is unable to utilize lactose as a carbon source.  He conducts an Hfr conjugal mating between *Escherichia coli* 0AT-M1LK and *Escherichia coli* CR3AM, a *lacZ***+** positive bacteria.  He then selects for *Escherichia coli* 0AT-M1LK that can utilize lactose.  Which of the following statements correctly describes the new genotype of *Escherichia coli* 0AT-M1LK?

  

*Escherichia coli* 0AT-M1LK is now *lacZ***+** and F+. 

\
*Escherichia coli* 0AT-M1LK is now *lacZ***+** and F**-**. 

  

*Escherichia coli* 0AT-M1LK is *lacZ****-*** and F**+**.

  

*Escherichia coli* 0AT-M1LK is still *lacZ****-*** and F**-**

*Escherichia coli* 0AT-M1LK is now *lacZ***+** and F**-**

True or False: Release of an animal virus from a host cell always requires lysis of the host cell.

  

True

 

False

false

The first self-replicating biological systems were most likely composed of:

  

DNA

  

RNA

  

Lipid

 

Protein

RNA

The earliest energy generating metabolism of primitive cells was exclusively:

  

oxygenic.

  

aerobic.

  

photosynthetic.

 

anaerobic

anaerobic

A mutant that has a nutritional requirement for an amino acid (the amino acid needs to be supplied in the media) for growth is an example of a(n):

  

organotroph.

  

auxotroph.

  

autotroph.

 

heterotroph

auxotroph

Error-proof repair mechanisms are ____ fidelity and utilize _____________ to synthesize new DNA and _____________ ligate new repaired DNA to the chromosome.

  

low, DNA polymerase, RecA

  

high, DNA Polymerase I, DNA ligase

  

low, DNA Polymerase V, DNA ligase

 

high, DNA Polymerase III, DNA ligase

high, DNA polymerase I, DNA ligase

_____________  are mutations that occur due to agents in the environment or through deliberate manipulation by humans.

  

Non-selectable mutations

  

Spontaneous mutations

 

Induced mutations

  

Selectable mutations

induced mutations

Dr. Strummer is studying ampicillin resistant (AmpR), non-pathogenic bacterial species, *Bacillus cereus*.  He hypothesizes that he can make this organism pathogenic by mixing it with a pathogenic species of bacteria.  In experiment 1, Dr. Strummer infects mice with a tetracycline resistant (TetR), pathogenic bacterial species, *Bacillus anthracis*.  He harvests fluids from the sick mice that contain live *Bacillus anthracis* and mixes this fluid with *Bacillus cereus*.  He grows the mixture on agar plates containing ampicillin.  He then infects mice with *Bacillus cereus* from these plates.  The mice become sick.

In experiment 2, he isolates fluids from sick mice infected with *Bacillus anthracis*.  He filters the fluids through a filter that removes all live bacteria, but allows small molecules __**and**__ bacteriophage to remain in the fluid.  He then mixes the fluid with *Bacillus cereus* and plates on the mixture on agar plates containing Amp.  He infects mice with *Bacillus cereus* from these plates.  To his surprise the mice do not get sick.

What horizontal gene transfer process is responsible for *Bacillus cereus* becoming pathogenic in Dr. Strummer’s first experiment?

\
\
Transformation

\
Transmutation

\
Transduction

\
Conjugation

conjugation

Molecular Phylogeny uses the sequence of ___________ to determine the evolutionary relatedness of different organisms.

\
siRNA genes

\
rRNA genes

\
tRNA genes

\
Proteins

rRNA genes

How do bacteriophage influence bacterial evolution?

  

Bacteriophage cause cleavage and rearrangement of bacterial genomes, thus accelerating bacterial evolution.

  

Bacteriophage lyse mutated bacterial cells, thus preventing them from replicating and passing on their genetic information.

 

Bacteriophage transfer genetic information between bacterial cells through transduction, thus increasing the genetic diversity of bacterial populations.

  

Bacteriophage decrease the size of bacterial populations and thus decreasing genetic diversity and slowing down bacterial evolution.

bacteriophage transfer genetic information between bacterial cells through transduction, thus increasing the genetic diversity of bacterial populations

Most mutations are ________.  They ____________.

  

spontaneous, change both the genotype and the phenotype of the organism.

  

conditional, only change the phenotype of the organism under specific conditions.

  

silent, have no effect on the phenotype of the organism.

 

selectable, change the phenotype of the organism

silent, have no effect on the phenotype of the organism