Unit 3 Practice Exam #1

__________ prevent transcription, whereas __________ stimulate transcription.

A) Activators; repressors

B) Inducers; corepressors

C) inactive repressors; active repressors

D) Regulators; repressors

E) Repressors; activators

E) Repressors; activators

Which of the following is not a method of horizontal gene transfer?

A) formation of daughter cells

B) conjugation

C) integration of a plasmid into the host chromosome

D) transformation

E) All the above are examples of horizontal gene transfer

A) formation of daughter cells

A particular animal virus requires the use of DNA polymerase from its host, since it does not possess its own DNA polymerase enzyme. Which of the following assumptions in A-D would likely be correct regarding this virus?

A) This virus could not be a retrovirus type.

B) It could be a (-) ss RNA virus.

C) It could be a (+) ss RNA virus.

D) The virus life cycle very likely includes going to the host cell nucleus.

E) All of A-D are correct assumptions.

D) The virus life cycle very likely includes going to the host cell nucleus.

Using the figure above as a guide, along with your knowledge of bacterial genomes, you can be certain that for one of the E. coli cells residing in your gut that

A) it will possess more than 10,000 genes

B) it will be identical to the other E. coli cells in your gut

C) its genome may comprise one or more plasmids in addition to the chromosome

D) it will have exactly 4721 genes total

E) two of the above are correct

C) its genome may comprise one or more plasmids in addition to the chromosome

Genomic islands

A) contain genes of similar function

B) typically represent the flexible gene pool of a bacterial population

C) may possess genes related to pathogenicity or symbiosis

D) are typically acquired by horizontal gene transfer

E) All the above are correct

E) All the above are correct

Which statement among A-C is false concerning the M13 filamentous bacteriophage?

A) it can form a prophage

B) it does not kill the host cell

C) because of the life cycle it possesses, it can generally always be sure to have a host cell(s) to infect

D) None are A-C is false; all are true statements

A) it can form a prophage

The attenuation mechanism that helps block expression of the tryptophan operon requires all of the following, except

A) mRNA transcript of the trp leader sequence

B) a ribosome stalled at the tryptophan codons of the trp leader transcript

C) formation of an attenuator loop

D) high intracellular levels of tryptophan

B) a ribosome stalled at the tryptophan codons of the trp leader transcript

Part of the mechanism of specialized transduction resembles the formation of an F prime factor.

A) True

B) False

A) True

A bacterium's genome possesses catabolic genes X, Y, and Z; if it later conjugates and receives a plasmid containing genes X and Y you would consider this bacterium to be

A) diploid

B) defective

C) a partial diploid

D) constitutive

E) haploid

C) a partial diploid

Which of the following among A-D is false regarding prokaryotic genes and genomes?

A) Prokaryotes are generally diploid cell types.

B) The structural genes of an operon are the functional genes common to a particular cellular function or pathway.

C) Promoters and operators are DNA sequences that non-protein coding sequences.

D) Most prokaryotic genes transcripts are generally polycistronic mRNAs.

E) None of A-D is false

A) Prokaryotes are generally diploid cell types.

The CRISPR system of bacteria:

A) is an operon consisting of several genes.

B) is a type of bacterial immune system to defend against viruses.

C) facilitates the horizontal transfer of genes.

D) allows a prophage to form.

E) all are applicable to the CRISPR system of bacteria

B) is a type of bacterial immune system to defend against viruses.

What is the phenotype of an E. coli strain with a mutation in the lac operator that prevents the lac repressor from ever binding? Assume glucose is absent.

A) Transcription of the operon is very high whether lactose is present or not.

B) Transcription of the operon is very low whether lactose is present or not.

C) Transcription of the operon is high in the presence of lactose, and low in its absence.

D) Transcription of the operon is low in the presence of lactose, and high in its absence.

A) Transcription of the operon is very high whether lactose is present or not.

The following are true among A- D concerning transposons EXCEPT

A) they have a transposase gene

B) they possess insertion sequences

C) they possess inverted repeat sequences

D) they have the ability to "jump" within the same chromosome

E) No exceptions, A - D comprise all transposons

E) No exceptions, A - D comprise all transposons

Which of the following is false regarding all types of viruses:

A) they all have either RNA or DNA

B) they all have a coat of capsid proteins surrounding their nucleic acid

C) they all can take in and metabolize food sources for energy

D) they all require a host to replicate

E) None of A-D are false; they are all true statements.

C) they all can take in and metabolize food sources for energy

When both glucose and lactose are added to the growth medium, Escherichia coli will have a growth curve that:

A) does not change

B) grows slowly and then, halfway through, grows faster

C) grows, levels off, and then grows again

D) grows more slowly than with glucose alone

E) grows more quickly than with glucose alone

C) grows, levels off, and then grows again

Antisense RNAs DO NOT

A) occur in protein coding genes

B) affect expression of several protein coding genes in a cell

C) bind to mRNA

D) act as translational control mechanism

B) affect expression of several protein coding genes in a cell

Which statement is true regarding prions and viroids?

A) Viruses have capsids composed of protein, whereas viroids have no capsids.

B) Prions are infectious proteins, and lack nucleic acids.

C) Viroids are comprised only of RNA.

D) Prions can cause a degenerative neurological disease in humans and other mammals, whereas viroids primarily infect plants.

E) All are true.

E) All are true.

A reduction in growth rate that occurs during conditions of nutrient limitation can result in bacteria eliciting the stringent response, a mechanism that helps to conserve energy by reducing ____________ via alteration of the transcription of certain genes.

A) inducer levels

B) ribosome formation and assembly

C) repressor activation

D) carbon uptake

B) ribosome formation and assembly

Which choice among A -D is not applicable to the heat shock response?

A) It is a post-transcriptional/translational control mechanism.

B) It can result in the expression of different chaperone proteins.

C) A specific sigma factor is expressed at elevated temperature.

D) Ribosomes cannot efficiently translate the heat shock specific sigma factor transcript at ambient temperatures.

E) A -D are all applicable.

E) A -D are all applicable.

Naked viruses

A) lack a capsid

B) are missing glycoproteins on their surface

C) do not have a membrane covering their capsid

D) are inferior to non-naked viruses

E) are not infectious

C) do not have a membrane covering their capsid

Which statement is applicable to plasmids?

A) They may duplicate themselves by rolling circle replication.

B) They replicate only when the cell's chromosome replicates prior to cell division.

C) Plasmids typically carry hundreds of genes, usually of multiple metabolic pathways.

D) None of the above is applicable to plasmids.

A) They may duplicate themselves by rolling circle replication.

Which of the following is false regarding an Hfr strain?

A) During conjugation, an F- recipient cell can receive part of the chromosome from an Hfr donor.

B) In general, conjugation with an Hfr strain does not typically convert the F- recipient to an F+ cell.

C) An Hfr strain forms as the result of transformation.

D) Hfr strains can be used to map the genes on the chromosome of the Hfr strain.

E) An F prime factor can originate from an Hfr strain

C) An Hfr strain forms as the result of transformation.

Which statement among A-D is false regarding animal viral infections?

A) Uncoating refers to the process of releasing the genome from the viral capsid.

B) Assembly of new viruses can only occur in the cytoplasm.

C) Budding is a mechanism of virus exit that leads to acquisition of the envelope around the viral particles.

D) Endosome formation and cell membrane fusion are mechanisms that allow for uncoating of the virus.

E) none of A-D are false

B) Assembly of new viruses can only occur in the cytoplasm.

Which of the following would be involved in some part of the process of translation of a bacterial gene?

A) sigma factor

B) Shine-Delgarno sequence

C) promoter

D) operator

E) none of the above is correct; all are involved in transcription

B) Shine-Delgarno sequence

Which is false regarding recombination?

A) It can occur between a cell’s chromosome and DNA acquired via conjugation, transduction, or transformation.

B) It requires RecA protein to scan for homology between the chromosome and acquired DNA.

C) It results in the formation of Holiday structures.

D) None are false; all are true regarding recombination.

D) None are false; all are true regarding recombination.

Which statement is false concerning retroviruses:

A) The information flow of such viruses is: RNA to DNA to RNA to protein.

B) They can form a provirus.

C) They can remain in the provirus state while simultaneously initiating production of new viral particles.

D) None of A-C are false; they are all true statements.

D) None of A-C are false; they are all true statements.

Transformation:

A) is the process by which a bacterium converts genetic information into a protein

B) is a process which may lead to a bacterium becoming a pathogen or resistant to an antibiotic.

C) is how polyribosome formation occurs

D) is the process that occurs following promoter recognition

E) none of the above is correct

B) is a process which may lead to a bacterium becoming a pathogen or resistant to an antibiotic.

Which of the following among A - D is false regarding small regulatory RNAs (sRNA)?

A) They do not code for proteins.

B) They occur between genes.

C) They act on RNA transcripts.

D) They can act as a translational control mechanism.

E) A - D are all true.

E) A - D are all true.

Bacterium X has acquired an F prime factor from bacterium Y via conjugation. This means that

A) bacterium X has acquired a gene or genes from the chromosome of bacterium Y.

B) bacterium X has undergone transduction.

C) a small portion of bacterium Y's chromosome now has a deletion.

D) bacterium Y is now an F- strain.

E) Two of the above are correct.

E) Two of the above are correct.

High levels of transcription of the lactose operon require all of the following, EXCEPT:

A) the presence of lactose

B) high levels of cAMP (cyclic AMP)

C) the absence of glucose

D) the formation of allolactose

E) A-D are all required

E) A-D are all required

Which of the following directly relates to viral tropism?

A) the different types of cells/tissue the virus can infect in a host

B) recognition of protein/glycoprotein receptors on the surface of the host cell(s)

C) the mode of entry of the virus

D) capsid type of the virus

E) two of the above are correct

A) the different types of cells/tissue the virus can infect in a host

Which of the following is not true of phase variation?

A) The orientation of the DNA sequence is inverted.

B) It may help the bacteria avoid the immune system.

C) It requires recombination.

D) It affects external structures of the bacterium, like the flagellum, capsule, or fimbriae.

E) All are true

E) All are true

The -35 and -10 consensus sequences upstream from the transcription start site are

A) located in the mRNA transcript.

B) used for ribosome binding.

C) needed for rolling circle replication.

D) where the start codon for translation is located.

E) None of the above is correct

E) None of the above is correct

Which of the following statements is true regarding the lysogenic cycle of lambda phage?

A) After infection, the viral genes immediately turn the host cell into a lambda phage-producing factory, and the host cell then lyses.

B) The prophage does not allow the host cell to grow and divide.

C) The phage genome replicates along with the host genome.

D) The lysogenic state is permanent.

E) All the above are true.

C) The phage genome replicates along with the host genome.

Which of the following is not needed for bacterial transcription?

A) a ribosome-binding sequence

B) a promoter

C) core RNA polymerase function

D) sigma factor

E) all are needed for transcription

A) a ribosome-binding sequence

The absence of tryptophan (trp) in E. coli

A) produces an active trp repressor

B) causes tryptophan to act as an inducer of transcription of the trp operon

C) prevents transcription of the trp structural genes

D) none of the above is correct

D) none of the above is correct

BONUS Which of the following is composed only of DNA?

A) An inducer

B) An operator

C) A a corepressor

D) A repressor

E) An activator

B) An operator