Micro Exam 3 Homework Q's

Translation requires the use of:

mRNA, tRNA, rRNA

Most sigma factors are highly conserved and help RNA polymerases identify the beginning of genes. They accomplish this by binding to which of the following sites on promoters?

-10 and -35 sites

A 10 base-pair deletion occurs in the promoter sequence of a gene. What is the most likely effect on the transcription level of the gene?

transciption of the gene is reduced

Most tRNAs become charged with

an amino acid

_________ is responsible for the catalytic activity of the ribosome

rRNA

In _________ translation of mRNA can begin before transcription of the mRNA is completed

prokaryotes

Dr. Strummer experimentally changes the DNA sequence directly upstream of a translation start codon of genX in E. coli to investigate the function of this region of DNA. Experiments reveal that after the change the same amount of genX mRNA is made from the operon, but there are very no GenX protein is made. What is the most likely function of the nucleic acid sequence that Dr. Strummer changed?

the sequence likely functions as a ribosome-binding site

Antibiotics inhibit translation during the ______ step(s).

initiation and elongation

Which of the following factors is NOT required for translation initiation?

RnaseH

Dr. Strummer is investigating a new strain Escherichia coli with a mutation in the 5th codon of ArgR, the arginine operon repressor protein. The mutation changes the DNA code so that the mRNA code reads UAG rather than UCG. Which of the following statements best describes the effect of the mutation:

the bacteria is unable to repress transcription of the arginine biosynthesis operon

Which of the following statements about the bacterial ribosome is FALSE?

the prokaryotic ribosome is composed of two subunits, 60s and 40s that bind each other to form the complete ribosome

What is the role of the Beta Subunit of RNA polymerase?

catalyze the joining of ribonucleic acids

Which sentence correctly describes inducers and co-repressors?

both interact with a cognate repressor to regulate trancription of an operon

lacO is:

a sequence of DNA in the lactose operon promoter

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:

the 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

DNA binding proteins interact with the _____ of the DNA double helix _______:

major groove...at a specific sequence of nucleotides

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

low...cyclic AMP

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

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 positive regulator of heat shock gene expression

Dr. Strummer is working with an E. coli strain that has a mutation in the araC gene. This mutation causes the AraC protein to no longer be able to bind arabinose. How would this mutation effect the expression of the arabinose operon in conditions of low glucose and high arabinose?

the arabinose operon would be expressed at a low level

Quorum Sensing is:

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

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

is phosphorylated and then interacts with the promoter of an operon

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 sense the change in extracellular salt concentrations

In nutrient poor conditions, stalled ribosomes increase the production of _____. This secondary messenger reduces the ________ resulting in fewer _____.

ppGpp...transcription of rRNA genes...ribosomes

Anti-sigma factors regulate gene expression by:

binding reversibly to their target sigma factors to prevent their association with RNA polymerase.

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

phospholipids...host proteins

Compared with cellular genomes, viral genomes:

are smaller...with fewer base pairs

True or False

After uncoating, a single-strand, positive sense DNA viral genome can be directly transcribed by host cell RNA polymerases.

False

Which of the following viral activities is not observed during the eclipse period of the viral life cycle?

release of virions from the host cell

A temperate bacteriophage:

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

Lambda (λ) phage infects a bacteria growing in nutritionally rich growth media. Which of the following statements is TRUE.

Lambda phage will enter the lytic cycle due to low levels of CII, which is a direct positive regular of CI repressor expression

The late genes of the T4 genome encode:

capsid, assembly and release proteins

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

false

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

induced mutations

Most mutations are ________. They ____________.

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

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?

missense mutation

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):

auxotroph

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

initiation of endospore formation by Bacillus subtillis during nutrient limitation

How do bacteriophage influence bacterial evolution?

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

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

transformation...conjugation

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

high...DNA polymerase I...DNA ligase

Which of the following DNA repair mechanisms is error prone?

SOS repair

True or False

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

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?

E. coli OAT-MILK is now lacZ+ and F-

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 mixes a liquid culture of Bacillus anthracis and liquid culture of Bacillus cereus for 24 hours. 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, Dr. Strummer filters a liquid culture of Bacillus anthracis through a filter that removes all live bacteria, but allows small molecules and bacteriophage to remain in the fluid. He mixes the filtered fluid with Bacillus cereus, incubates the mixture for 24 hours, and then 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?

conjugation