Deck 21: Transcription and Rna Processing

Question 1

A consensus sequence

A) is a hypothetical sequence.
B) indicates the nucleotides most commonly found at each position.
C) describes the most efficient promoter sequence for the RNA polymerase holoenzyme.
D) All of the above

Answer 1

All of the above

Question 2

Which of the following is true for the unwinding of the DNA helix and the synthesis of a short stretch of RNA?

A) The process requires a helicase and a primase as in DNA replication.
B) In transcription, these steps proceed via an RNA polymerase holoenzyme.
C) The unwinding and subsequent synthesis above serve as a primer for chain elongation.
D) All of the above

Answer 2

All of the above

Question 3

The template strand of DNA is copied by RNA polymerase from

A) both 3ʹ → 5ʹ and 5ʹ → 3ʹ ends.
B) 5-10 nucleotides before the +1 transition site.
C) 3ʹ → 5ʹ end.
D) 5ʹ → 3ʹ end.

Answer 3

3ʹ → 5ʹ end.

Question 4

What does it mean to say that the most common type of promoter in E. coli is bipartite?

A) The promoter region is divided into two parts which flank the sequence for the gene.
B) There are two separate regions of sequence similarity in the promoter.
C) The sequence of the promoter has dyad symmetry.
D) The promoter must bind two RNA polymerase holoenzymes to transcribe the gene.

Question 5

RNA polymerase uses the strand of DNA in transcription.

A) sense
B) antisense
C) coding
D) un-coded

Question 6

Which of the following is correct?

A) Transcription proceeds in the 5ʹ → 3ʹ direction.
B) The template strand is copied from the 5ʹ end to the 3ʹ end.
C) RNA polymerization proceeds in the 3ʹ → 5ʹ direction.
D) None of the above

Question 7

Transcription termination

A) occurs at certain DNA sequences where the elongation complex is unstable.
B) sometimes requires a specific protein, rho, which facilitates disassembly.
C) often occurs near pause sites.
D) All of the above

Question 8

When a sequence of double-strand DNA is displayed

A) the coding strand is written in the 3ʹ → 5ʹ direction.
B) the template strand is written in the 5ʹ → 3ʹ direction.
C) the coding strand is identical to the RNA product.
D) None of the above

Question 9

Which of the following is true about transcription?

A) Promoters are regions of DNA which serve as transcription initiation sites.
B) Initiation is the rate-limiting step in transcription.
C) Each gene, in eukaryotic cells, usually has its own promoter.
D) All of the above

Question 10

The type of RNA that is least stable in cells is .

A) tRNA
B) rRNA
C) mRNA
D) small RNA

Question 11

The sigma-70 subunit

A) increases the affinity of the core polymerase for nonpromoter sequences.
B) decreases the affinity of the core polymerase for specific promoter sequences.
C) is responsible for transcribing many genes.
D) is associated with a holoenzyme, enabling the formation of more stable complexes.
E) All of the above.

Question 12

Which is matched incorrectly?

A) RP_o-RNA polymerase at a transcription bubble of DNA
B) RP_c-RNA polymerase bound to single-stranded DNA
C) NusA -helps convert RNA polymerase to an elongation form
D) s-protein factor aiding promoter binding

Question 13

For an RNA hairpin loop to form, the transcribed region of the DNA sequence must .

A) be a palindrome
B) have dyad symmetry
C) contain an intron
D) have a tandem repeat

Question 14

Which is not a property of RNA polymerase?

A) polymerizes in the 5ʹ → 3ʹ direction
B) catalyzes the formation of phosphodiester linkages
C) polymerizes a reaction assisted by pyrophosphate hydrolysis
D) has exonuclease proof-reading activity

Question 15

Which statement about RNA polymerase is false?

A) The large beta subunit comprises the active site of the enzyme.
B) The alpha subunits are the scaffold for assembly of the other subunits.
C) The role of the omega subunit is well characterized.
D) All of the above are false

Question 16

Francois Jacob and Jacques Monod are responsible for

A) discovering that the sequence of an mRNA molecule is complementary to a segment of one of the DNA strands.
B) predicting the ʺcentral dogmaʺ of molecular biology.
C) proposing that a single unit of heredity directed the production of a single enzyme.
D) All of the above

Question 17

Which of the following is true, concerning rho?

A) It is a heptameric protein with potent ATPase activity.
B) It has an affinity for single-stranded DNA .
C) It may function as an RNA-DNA helicase.
D) None of the above

Question 18

Which of the following are correct matches for the given genes?

A) rpoN : nitrogen metabolism
B) rpoH : heat shock
C) Gene 55 : bacteriophage T4
D) All of the above

Question 19

Which subunit of the E. coli core RNA polymerase a₂bbʹw) contributes to DNA binding?

A) a
B) b
C) bʹ
D) w

Question 20

Rho-dependent termination

A) is due to destabilization of the RNA-DNA hybrid.
B) is due to indirect contact between the transcription complex and rho as rho binds RNA.
C) may cause the RNA polymerase to bind to template DNA.
D) All of the above

Question 21

Constitutive genes

A) have products that are maintained at constant levels.
B) are genes expressed by all cells.
C) are transcribed continuously.
D) All of the above
E) None of the above

Question 22

Protein X is found to bind to a certain geneʹs promoter only when substance A is not present. The gene can be transcribed in the presence of both X and A. It is not transcribed in the presence of X alone. Protein X is a/an . Substance A is a/an .

A) repressor; inducer
B) repressor; corepressor
C) activator; inducer
D) activator; corepressor

Question 23

Which statement is false concerning the general transcription factor, TFIID?

A) It binds to the promoter.
B) Its TBP subunit binds to the region containing the TATA box.
C) It interacts with TFIIA in the presence of DNA.
D) It is the RNA polymerase II initiation factor.
E) None of the above

Question 24

Which of the following is/are true concerning TAFs and TBP?

A) They are subunits of TFIIB and TFIID, respectively.
B) TBP is required to initiate transcription of class I and class III genes .
C) They are not associated with RNA polymerase I and RNA polymerase III.
D) All of the above

Question 25

Which statement is false about the utilization of lactose as a carbon source by E. coli?

A) In the presence of both glucose and lactose, the enzymes necessary for lactose catabolism are produced only in limited amounts.
B) Lactose is the inducer for the enzymes responsible for its own catabolism.
C) In the absence of lactose, the repressor binds to a single site upstream of the lac genes.
D) The catabolic enzymes are encoded in a three-gene operon controlled by a single promoter.

Question 26

Which statement is true about the relative number of accessory proteins necessary for RNA polymerization in eukaryotes versus E. coli?

A) Eukaryotes require many more accessory proteins.
B) They require about the same number of accessory proteins.
C) Eukaryotes require far fewer accessory proteins.
D) The number required varies widely by species. Some eukaryotes require less than E. coli and some require more.

Question 27

Which statement is not true about the TATA box?

A) The TBP portion of the general transcription factor TFIID binds to the TATA box forming a molecular clamp.
B) It is located about 19-27 bp upstream from the transcription start site of class II genes.
C) Its sequence is highly conserved among all species.
D) This region of DNA is more easily unwound to an open complex than other general sections of DNA.

Question 28

When a repressor protein is bound, unbound) to a promoter region transcription is bound, unbound) to a promoter transcription is

A) bound; unbound
B) unbound; bound
C) bound; bound
D) unbound; unbound

Question 29

Which observation is not evidence that supports the theory that mitochondria and chloroplasts originate from symbiotic bacteria?

A) Genes for both mitochondrial and chloroplast RNA polymerase are encoded in the DNA of these organelles.
B) Both mitochondria and chloroplasts are about the same size as bacterial cells.
C) Chloroplast RNA polymerase is similar in sequence to that of cyanobacteria.
D) Both mitochondria and chloroplasts have their own DNA.

Question 30

Which of the following is true about transcription?

A) A repressor protein activates transcription of a negatively regulated gene.
B) A positively regulated gene can be transcribed only in the absence of active repressor.
C) In the absence of an activator, a negatively regulated gene is poorly transcribed.
D) The initiation of transcription of regulated genes is controlled by regulatory proteins which bind to specific DNA sequences.
E) All of the above

Question 31

Which of the following is an incorrect association between RNA polymerase and its products?

A) RNA polymerase I : 35 - 47S pre-rRNA
B) RNA polymerase I: 5S rRNA
C) RNA polymerase II : mRNA precursors
D) RNA polymerase III : tRNA
E) None of the above

Question 32

Which statement is not true about the binding of TBP TATA binding protein)?

A) The TBP subunit is only required for the initiation of transcription of class II genes.
B) The binding of TBP to DNA distorts the DNA out of the standard B-DNA form.
C) Contacts between TBP and DNA are mainly in the minor groove.
D) TBP forms a saddle-shaped molecular clamp that surrounds DNA at the TATA box.

Question 33

Which of the following is an incorrect association between transcription factors and their characteristics?

A) TFIIB : interacts with RNA polymerase II.
B) SPI: binds to GC-rich sequence.
C) TFIIH: couples transcription to DNA repair.
D) TFIIE : recognizes the core sequence CCAAT.
E) All of the above

Question 34

The σ⁷⁰ subunit in E. coli RNA polymerase acts as a/an .

A) repressor
B) sliding clamp
C) helicase
D) initiation factor

Question 35

Characteristics of ligands involved in transcription include:

A) They can modify the function of repressors and activators.
B) They are considered inducers when they bind to repressors and activate them.
C) They are considered corepressors when they bind to repressors and inactivate them.
D) All of the above

Question 36

Positive regulation of a gene requires .

A) an activator protein
B) positive cooperativity
C) an allosteric inducer
D) the conversion of ATP to ADP and inorganic phosphate

Question 37

An extremely large lactose source is encountered by an E. coli cell in the lumen of the small intestine of a human who just ate an entire carton of ice cream. Which of the following would most likely be a contributor to why the E. coli does not metabolize any of the lactose?

A) presence of allolactose
B) presence of phosphorylated adenylate cyclase
C) absence of glucose
D) absence of cAMP

Question 38

An operon is .

A) a set of genes whose transcription is controlled by a single promoter
B) the site of repressor binding
C) a protein that activates the transcription of a whole class of genes
D) a multisubunit complex responsible for the splicing of exons

Question 39

The transcription of RNA accounts for most of the transcriptional activity of a cell.

A) transfer
B) ribosomal
C) messenger
D) heterogeneous nuclear

Question 40

Most of the RNA polymerase activity in eukaryotic cells occurs in the

A) cytoplasm.
B) mitochondria.
C) nucleolus.
D) nucleoplasm.

Question 41

Which has its primary transcript produced in the nucleolus?

A) tRNA
B) mRNA
C) rRNA
D) sRNA

Question 42

The sequence CCA must occur .

A) at the 3ʹ end of both prokaryotic and eukaryotic tRNA
B) immediately upstream from the TATA box
C) at the 5ʹ end of an intron
D) at the origin of replication in E. coli

Question 43

RNA polymerase catalyzes DNA-directed RNA synthesis.

Question 44

Which statement is false about operons that have the feature of catabolic repression?

A) Several different multisubunit repressors can block the transcription of such an operon.
B) Operons with catabolic repression have characteristically weak promoters.
C) Their transcription is lowered in the presence of glucose.
D) Transcription of such an operon is increased as the concentration of cAMP increases.

Question 45

A small percentage of the total RNA in a cell is ribosomal RNA.

Question 46

A transcription complex does not form when one or more proteins bind to the promoter sequence and to RNA polymerase in eukaryotes.

Question 47

Which is not part of the lac operon?

A) lacA
B) lacI
C) lacY
D) lacZ
E) None of the above; they are all part of the lac operon

Question 48

The unwinding of DNA at the initiation site is an example of a conformational change.

Question 49

Rho-dependent termination requires exposure of single-stranded RNA.

Question 50

Which is not generally associated with RNA processing?

A) addition of nucleotides
B) removal of nucleotides
C) covalent modification of bases
D) phosphorylation at the 3ʹ end

Question 51

A gene contains two 100 bp introns and three 50 bp exons. About how long is the mature RNA transcribed from this gene?

A) 75 bp
B) 150 bp
C) 200 bp
D) 350 bp
E) Cannot tell from the information given

Question 52

Sequences that are removed from the primary RNA transcript in eukaryotes are called .

A) introns
B) operons
C) exons
D) mRNA

Question 53

Which does not apply to the post-transcriptional processing of ribosomal RNA?

A) The subunits of rRNA are produced in equal amounts since they originate from the same transcript.
B) tRNA precursors are sometimes cleaved from the primary transcript of rRNA precursor.
C) A polyA tail is added to the 5ʹ end of the 30S subunit.
D) After initial cleavage of the primary transcript, specific endonucleases trim nucleotides from the ends of rRNA molecules.

Question 54

Which is not a feature of eukaryotic mRNA processing?

A) addition of a 5ʹ-5ʹ triphosphate linkage to GTP
B) methylation of the terminal CCA triad
C) addition of a polyA tail to the 3ʹ end
D) removal of intron sequences

Question 55

The product of the lacZ gene is .

A) lac repressor
B) β-galactosidase
C) thiogalactoside transacetylase
D) lactose permease

Question 56

Transcription is the process by which the information in mRNA molecules is interpreted and the appropriate proteins synthesized.

Question 57

The purpose of the GTP cap on mRNA is .

A) to prevent the formation of hairpin loops
B) to serve as a site for binding to the ribosome
C) to assist in the transport of mRNA out of the nucleus
D) to prevent exonuclease attack

Question 58

The large RNA-protein complex that processes introns and exons is called .

A) the replisome
B) the catalytic RNA complex
C) the spliceosome
D) RNA ligase

Question 59

RNA polymerase requires a high-precision fit when catalyzing the formation of a new phosphodiester linkage.

Question 60

Which is not true about the lac repressor?

A) Its gene is part of the lac operon and is transcribed along with lacZ, lacA and lacY.
B) When it binds to DNA, it forms a loop-type structure.
C) It likely blocks both RNA polymerase binding as well as transcription initiation.
D) It binds to DNA by interaction of an α-helix with the major groove.

Question 61

Post-transcriptional modification of mRNA in eukaryotes occurs after they are transported to the cytosol, but before they bind to the ribosome.

Question 62

TFIIB can bind to DNA in the absence of TFIID.

Question 63

The CRP-cAMP complex is an activator of the lac operon.

Question 64

Operons are a common gene arrangement found in all living organisms.

Question 65

All housekeeping genes have weak promotors and are regulated to maintain their gene products at constant low level concentrations.

Question 66

The same RNA polymerase that transcribes the ribosomal RNA transcribes all mitochondrial genes.

Question 67

Activators and repressors are often allosteric proteins.

Question 68

Mutations in sequences that are removed from the primary RNA transcript never affect RNA processing.

Question 69

Class I genes encode large ribosomal RNA.

Question 70

TATA binding protein is the only transcription factor common among all eukaryotic RNA polymerases.

Question 71

The gene products of the lacZ, lacA and lacY genes are specific for the hydrolysis of a different
β-galactoside sugar.

Question 72

Rho-dependent termination occurs at pause sites within the coding region.

Question 73

The genes encoding the chloroplast RNA polymerase are not similar in sequence to those of RNA polymerase in cyanobacteria.

Question 74

The splicing of exons does not occur in prokaryotes.

Question 75

Regulation of gene expression can only occur at the level of transcription.