Transcription of the Genetic Code: The Biosynthesis of RNA

Question 1

Which of following statements describes a difference between replication of DNA and transcription of RNA?
a. Nucleoside triphosphates are the precursors for replication, but nucleoside diphosphates are used for
transcription.
b. Both strands of DNA are copied in replication, but usually only one is copied in transcription.
c. Base pairing is used to copy the sequence in replication, but not in transcription.
d. The chain grows from the 5’ to the 3’ end in replication, but 3’ to 5’ in transcription.
e. None of these

Answer 1

b

Question 2

Which of following statements concerning RNA transcription is false?
a. The DNA strands become separated during synthesis.
b. Synthesis of RNA is as accurate as synthesis of DNA
c. The template strand is read in the 3’ → 5’ direction.
d. All 4 ribonucleotides are required.
e. A primer is required for RNA synthesis

Answer 2

b

Question 3

Which of following statements concerning RNA transcription is false?
a. The release of pyrophosphate from a nucleoside triphosphate drives the reaction.
b. RNA is synthesized from the 5’ end to the 3’ end.
c. DNA to RNA base pairing includes A to U and G to C.
d. Transcription requires the use of a primer.
e. None of these

Answer 3

d

Question 4

The enzyme principally responsible for RNA synthesis in Escherichia coli
a. is a multisubunit enzyme
b. consists of a single polypeptide chain
c. requires Mn2+ for activity
d. requires a DNA primer

Answer 4

a

Question 5

The end of the new mRNA molecule in E. coli. usually terminates in a string of A’s
a. True
b. False

Answer 5

b

Question 6

Which of the following correctly describes a difference between RNA & DNA polymerases?
a. RNA polymerases usually do not need a template, while DNA polymerases do.
b. DNA polymerases usually require a primer (i.e., they can only continue a strand, not start one), while most RNA polymerases do not.
c. RNA polymerases usually synthesize introns, while DNA polymerases synthesize cistrons.
d. RNA polymerases polymerize 5’ → 3’, while DNA polymerases polymerize 3’ → 5’.
e. None of these

Answer 6

b

Question 7

How do the core enzyme and the holoenzyme of RNA polymerase differ in E. coli?
a. The holoenzyme includes the sigma (σ) subunit, the core enzyme does not.
b. The core enzyme includes the sigma (σ) subunit, the holoenzyme does not.
c. The holoenzyme transcribes from an RNA template, the core enzyme from a DNA template.
d. The core enzyme transcribes from an RNA template, the holoenzyme from a DNA template.

Answer 7

a

Question 8

Which of these terms does not describe the DNA strand used to direct RNA synthesis?
a. Template strand
b. Coding strand
c. Antisense strand
d. Negative or “−” strand
e. All these terms describe the DNA strand used to direct RNA synthesis

Answer 8

b

Question 9

At what point does the sigma (σ) subunit of RNA polymerase released from the core enzyme?
a. Prior to the incorporation of any nucleotides into an RNA strand.
b. After transcription begins and about 10 nucleotides have been added to the RNA chain.
c. Just prior to chain termination.
d. Never; it is an intrinsic part of the core enzyme.
e. After RNA polymerase discovers an inverted repeat

Answer 9

b

Question 10

RNA synthesis begins at the base in the DNA sequence designated by the following number:
a. +1 (plus one)
b. 0 (zero)
c. −1 (minus one)
d. −10 region (minus ten)
e. It varies between genes.

Answer 10

a

Question 11

What is the function of the sigma (σ) subunit of RNA polymerase in E. coli?
a. It recognizes promoters where transcription should begin.
b. It contains the active site for synthesis of RNA.
c. It ensures proper processitvity of the polymerase, so it doesn’t stop prematurely.
d. It is involved in chain termination.
e. It scrunches the DNA

Answer 11

a

Question 12

Which of the following is not a property of the sigma (σ) subunit?
a. It tells the RNA Polymerase where to sit down.
b. It helps point the RNA Polymerase in the proper direction.
c. It causes the RNA Polymerase to bind tightly to the DNA.
d. It stays with the RNA Polymerase throughout synthesis.

Answer 12

d

Question 13

Which of the following is not part of the core promoter?
a. the transcription start site
b. the Pribnow box (−10 region)
c. the −35 region
d. the UP element

Answer 13

d

Question 14

The promoter site is
a. the start site for transcription in DNA
b. the binding site for regulatory proteins that stimulate transcription
c. the general region of DNA downstream from the start site
d. the site on DNA at which RNA polymerase binds to initiate transcription
e. None of these

Answer 14

d

Question 15

Which of the following offers the best description of a Pribnow box?
a. A promoter consensus sequence located at approximately −35.
b. A promoter consensus sequence located at approximately −10.
c. A sequence forming a hairpin loop signaling the termination of transcription.
d. A sequence immediately surrounding the start site of transcription.

Answer 15

b

Question 16

Initiation of RNA biosynthesis involves
a. recognition of the promoter region by the α subunit of RNA polymerase
b. conversion of the closed-promoter complex to the open-promoter complex
c. binding of one of the α subunits of RNA polymerase to each strand of DNA
d. incorporation of four pyrimidine nucleotides in succession

Answer 16

b

Question 17

Consensus sequences are
a. sequences that are invariant throughout the DNA.
b. sequences required for transcription to occur
c. sequences that have many bases in common
d. sequences that lie far upstream of the core promoter.

Answer 17

c

Question 18

What provides the energy for rho-dependent chain termination?
a. ATP hydrolysis distinct from any incorporation into the chain.
b. Nucleotide hydrolysis associated with incorporation into the chain.
c. Torsional stress built into the separating DNA strands.
d. There is no energy requirement

Answer 18

a

Question 19

Minor differences in the consensus sequence for RNA Polymerase
a. can be exploited to vary the amount of mRNA which is synthesized from that gene.
b. dictate the direction that RNA Polymerase proceeds from the promoter.
c. dictate whether sigma (σ) factor is required.
d. never occur.
e. have no effect on transcription

Answer 19

a

Question 20

Which of the following best describes the order of events at the promoter?
a. open complex → closed complex → transcription initiation
b. closed complex → open complex → transcription initiation
c. open complex → transcription initiation → closed complex
d. transcription initiation → open complex → closed complex

Answer 20

b

Question 21

What provides the energy for the conversion from the open complex to chain elongation?
a. ATP hydrolysis distinct from any incorporation into the chain.
b. Nucleotide hydrolysis associated with incorporation into the chain.
c. Torsional stress built into the separating DNA strands.
d. Binding of rho (ρ) factor to the holoenzyme.
e. None of these

Answer 21

c

Question 22

Chain termination occurs, in vivo, when:
a. RNA Polymerase gets to the end of the DNA.
b. The factor called rho (ρ) binds to the DNA.
c. A hairpin loop forms in the template.
d. Either a hairpin loop forms or rho (ρ) catches up with transcription stalled by a hairpin loop
e. None of these

Answer 22

d

Question 23

In prokaryotic RNA synthesis
a. the rate of incorporation of nucleotides is constant throughout the elongation process
b. the ρ (rho) protein is always required for termination
c. a unique series of three bases leads to termination
d. inverted-repeat sequences in the DNA being transcribed can lead to termination

Answer 23

d

Question 24

What is the need for a primer in transcription?
a. It ensures the fidelity of the newly synthesized RNA strand.
b. There is none.
c. RNA polymerases requires a preexisting strand with a nucleotide having a 3’−OH.
d. RNA polymerase requires a preexisting strand with a nucleotide having a 5’−OH.

Answer 24

b

Question 25

Which is not associated with bacterial promoters?
a. the transcription start site
b. the Pribnow box
c. the −35 element
d. 3’ antiterminator

Answer 25

d

Question 26

Which of the following is true concerning the first nucleotide incorporated into an RNA chain?
a. The first nucleotide incorporated into the RNA chain retains its 5’-triphosphate
b. The first nucleotide is always GMP
c. The first nucleotide is always cleaved off post-transcriptionally
d. The first nucleotide is always modified after transcription

Answer 26

a

Question 27

The weakness of A−U base pairs at the end of the RNA molecule may help in dissociation of the new RNA product.
a. True
b. False

Answer 27

a

Question 28

There is only one sigma subunit, since the same RNA Polymerase must bind to all genes in E. coli.
a. True
b. False

Answer 28

b

Question 29

How do enhancers differ from promoters?
a. Enhancers do not bind RNA polymerase.
b. Enhancers include the UP element.
c. Enhancers bind the sigma (σ) factor.
d. There is no difference; these terms are synonymous.

Answer 29

a

Question 30

Which of the following is the best description of an operon?
a. An enhancer that positively regulates gene expression.
b. An silencer that negatively regulates gene expression.
c. A binding element for the sigma (σ) factor.
d. A group of genes under the control of a common promoter.

Answer 30

d

Question 31

Operons
a. control the expression of constitutive genes.
b. are subject to positive or to negative control.
c. are not affected by mutations in the genes for repressors or inducers.
d. occur in both prokaryotes and eukaryotes.

Answer 31

b

Question 32

Which of the following influence the amount of expression of an operon?
a. Availability of the specific sigma factor for that operon.
b. How well the Pribnow box conforms to the consensus sequence.
c. Attenuation mechanisms.
d. Presence of 3’ 5’ cyclic AMP.
e. All of these.

Answer 32

e

Question 33

Which of the following does not influence the timing of expression of an operon?
a. Repressors
b. Co-repressors
c. Presence of substrates of the operon which need to be degraded
d. Inducers
e. All of these influence the timing of expression

Answer 33

a

Question 34

A mutation in the lac A gene would result in
a. continuous production of the proteins encoded by the three structural genes
b. continuous production of the lac repressor
c. normal operation of the lac operon, but with an alteration in the proteins encoded by the lac A gene
d. no transcription from the lac operon

Answer 34

c

Question 35

Cyclic AMP affects transcription by
a. triggering the action of several protein factors
b. phosphorylating a subunit of RNA polymerase
c. phosphorylating a transcription factor
d. inhibiting DNA looping
e. None of these

Answer 35

a

Question 36

A single operon
a. usually contains all the enzymes which are specific for the synthesis of a special biomolecule.
b. usually does not contain all the enzymes which are specific for the synthesis of a special biomolecule.
c. usually contains only a single structural gene for a critical enzyme.
d. usually contains only a gene for a repressor.

Answer 36

a

Question 37

All of the following apply to attenuation mechanisms, except:
a. They are used most often for operons for amino acid synthesis.
b. They involve the synthesis of proteins in the regulation of RNA synthesis.
c. The rate of RNA synthesis is regulated by the conformation of the protein being synthesized.
d. They require the presence of partially completed mRNA molecules.
e. All of these apply to attenuation mechanisms.

Answer 37

c

Question 38

Which of the conditions would result in the GREATEST amount of transcription of the lac operon?

 [glucose] [lactose] a.)     high         high b.)     low           low c.)     high          low d.)     low           high

Answer 38

d

Question 39

Attenuation mechanisms rely on alternative secondary structures forming in the mRNA.
a. True
b. False

Answer 39

a

Question 40

Which of the following is not a characteristic of catabolite activator protein (CAP)?
a. it is a positive regulator of the lac operon
b. when the cell has sufficient glucose and lactose, CAP will not be bound to the CAP binding site
c. CAP binding near the promoter site depends on CAP complexation with cAMP
d. the binding of CAP to DNA requires ATP hydrolysis

Answer 40

d

Question 41

Which of the conditions would result in the LEAST amount of transcription of the lac operon?

 [glucose] [lactose] a.)     high         high b.)     low           low c.)     high          low d.)     low           high

Answer 41

c

Question 42

Control of transcription in prokaryotes does not involve
a. enhancers.
b. silencers.
c. leucine zipper proteins.
d. alternative σ factors.

Answer 42

c

Question 43

Inducers for operons are often structurally related to the enzyme substrates of that operon.
a. True
b. False

Answer 43

a

Question 44

Inducers allow for a system in which an enzyme is not made unless it is needed.
a. True
b. False

Answer 44

a

Question 45

The catabolite activator protein can overcome the effect of a repressor binding to the operon.
a. True
b. False

Answer 45

a

Question 46

Which of the following is true about riboswitches:
a. They have a molecule sensing domain called an aptamer
b. There are known pathogens that use riboswitches as part of their mechanism
c. They respond to specific molecules and control translation in a way that is often similar to transcription
attenuation
d. They contain a sensing domain and a decision making domain
e. All of these

Answer 46

e

Question 47

Which of the following statements about eukaryotic and prokaryotic RNA polymerases, is false?
a. There are 3 different RNA polymerases in eukaryotes, instead of just one.
b. Eukaryotic polymerases have the same number of subunits as prokaryotic ones.
c. Only prokaryotic polymerases use sigma factor.
d. The enzymatic mechanism is the same for both types of organisms.

Answer 47

b

Question 48

Which enzyme transcribes genes encoding tRNA in eukaryotes?
a. RNA polymerase I
b. RNA polymerase II
c. RNA polymerase III
d. Different tRNAs are transcribed by different RNA polymerases.

Answer 48

c

Question 49

Which of the following is not a key step in the activation of mRNA synthesis in eukaryotes?
a. Binding of TBP to the DNA.
b. Binding of other transcription factors.
c. Binding of RNA Pol I.
d. Phosphorylation of the RNA Pol.
e. All of these are necessary to initiate RNA synthesis in eukaryotes.

Answer 49

c

Question 50

Which of the following statements about the various RNA Polymerases in eukaryotes is false?
a. Permanent RNAs, such as tRNA and rRNA use different RNA Polymerases.
b. The different RNA Polymerases share some subunits.
c. The RNA Polymerase for mRNA is designated RNA Pol II.
d. Eukaryotic RNA polymerases are generally monomeric

Answer 50

d

Question 51

How do eukaryotic and prokaryotic RNA polymerases compare?
a. Since eukaryotic RNA polymerases are more complex, little homology has been found between the actual
protein sequences in the catalytic subunits.
b. Since eukaryotic transcription is less complex than in prokaryotes, monomeric RNA polymerases are used.
c. Despite their added complexity, eukaryotic and prokaryotic RNA polymerases are generally homologous.
d. Eukaryotic and prokaryotic RNA polymerases are virtually identical

Answer 51

c

Question 52

Where is the TATA box located?
a. At the transcription start site (+1).
b. −10 region.
c. −25 region.
d. −40 region.

Answer 52

c

Question 53

TATA-binding protein (TBP) is normally required for transcription by
a. Pol I.
b. Pol II.
c. Pol III.
d. all of these polymerases.
e. none of these polymerases

Answer 53

d

Question 54

Phosphorylation of the CTD of RNA polymerase II occurs during which phase of transcription?
a. initial binding to the promoter
b. conversion from the closed complex to the open complex
c. termination of transcription
d. None of these

Answer 54

b

Question 55

Transcription in eukaryotes differs from RNA synthesis in prokaryotes
a. by requiring a primer.
b. by simplifying the process with multifunctional enzymes.
c. in using more complex σ factors.
d. by having multiple RNA polymerases rather than one.

Answer 55

d

Question 56

RNA polymerases from prokaryotes and eukaryotes
a. have sequence homology in catalytic subunits
b. have identical σ factors
c. differ because there is no analogue to the prokaryotic α subunit in eukaryotes
d. have the same number and kind of subunits

Answer 56

a

Question 57

A transcription factor is
a. a subunit of RNA polymerase II that does not have a prokaryotic analogue.
b. the part of the promoter sequence closest to the start of transcription.
c. a protein other than RNA polymerase that is involved in transcription.
d. a sequence that determines whether an upstream element will be an enhancer or silencer.

Answer 57

c

Question 58

Initiation of transcription in eukaryotes is primarily controlled
a. by two transcription factors
b. by keeping the TATA-binding protein physically separated from other transcription factors
c. by the order of binding of TFIIA and TFIIB
d. in the formation of the preinitiation complex

Answer 58

d

Question 59

The eukaryotic TATA-binding protein (TBP) functions in a manner similar to
a. sigma (σ) factor in E. coli.
b. rho (ρ) factor in E. coli.
c. lac I in E. coli.
d. CAP in E. coli.

Answer 59

a

Question 60

Which of the following transcription factors is involved in the elongation phase of eukaryotic transcription?
a. TFIIA
b. TFIID
c. TFIIF
d. There are no transcription factors associated with elongation.

Answer 60

c

Question 61

The elongation and termination phases of eukaryotic transcription
a. require several protein factors
b. are better understood than the initiation phase
c. are not subject to control mechanisms, only the initiation phase
d. proceed at a constant rate and always stop at the same termination sequence

Answer 61

a

Question 62

Which of the following is not true?
a. The mechanism of activation of eukaryotic genes involves addition and removal of phosphate residues from
some of the transcription factors.
b. In plants, there are 5 RNA polymerases.
c. RNA Pol IV is the primary RNA synthesizer in plants
d. Of the RNA Polymerases in eukaryotes, Pol II is the most extensively studied.

Answer 62

c

Question 63

The major difference between RNA initiation in eukaryotes and prokaryotes is the number of factors involved in the
process.
a. True
b. False

Answer 63

a

Question 64

General transcription activation in eukaryotes requires
a. a specific enhancer common to all genes
b. a specific silencer common to all genes
c. a protein called Mediator
d. a CREB binding protein
e. none of these

Answer 64

c

Question 65

Response elements
a. are similar to operons in that they are controlled by a single promoter
b. are enhancers of transcription activated by metabolic factors
c. are not affected by steroids
d. are silencers of transcription triggered by the presence of metal ions

Answer 65

b

Question 66

Which of the following is true?
a. Mediator is a giant complex with a mass over 1 million Daltons
b. Mediator contains many subunits called Med proteins
c. Mediator bridges the RNA Polymerase at the promoter region with enhancers
d. Mediator is the ultimate regulator of eukaryotic transcription
e. All of these

Answer 66

e

Question 67

As in prokaryotes, the regulatory regions for eukaryotic genes:
a. may be close to the genes they control
b. may be upstream of the genes they control
c. may be downstream of the genes they control
d. All of these are true

Answer 67

d

Question 68

Intracellular levels of cyclic AMP can affect the phosphorylation of proteins and enzymes as a secondary messenger.
a. True
b. False

Answer 68

a

Question 69

RNA transcribed from the coding strand instead of the template strand
a. is called antisense RNA.
b. produces histones.
c. is tRNA.
d. never occurs.

Answer 69

a

Question 70

Proteins that recognize DNA with specific base sequences are
a. more likely to bind to the major groove.
b. more likely to bind to the minor groove.
c. equally likely to bind to the major or minor grooves.
d. never occur.

Answer 70

a

Question 71

The leucine zipper is different from other DNA binding domains, since it requires the DNA-binding protein to form a
dimer.
a. True
b. False

Answer 71

b

Question 72

DNA binding domains are distinct from transcription-activation domains.
a. True
b. False

Answer 72

a

Question 73

Which of the following is not a structural motif encountered in DNA-binding proteins?
a. helix-turn-helix
b. leucine zipper
c. zinc finger
d. β−barrel

Answer 73

d

Question 74

CREB contains the following structural motif:
a. Helix-turn-helix
b. β−barrel
c. Zinc finger
d. Leucine zipper

Answer 74

d

Question 75

Which of the following best describes leucine zipper motifs?
a. They allow protein-protein interactions via hydrophobic bonds.
b. They allow protein-protein interactions via hydrogen bonds.
c. They allow protein-protein interactions via electrostatic interactions.
d. They allow protein-DNA interactions by fitting into the major groove of DNA.

Answer 75

a

Question 76

Which of the following is not a common modification occurring after polymerization of RNA?
a. Methylation of bases.
b. Addition of phosphate to the bases.
c. Removal of bases from the polymer.
d. Addition of bases to the polymer.
e. All of these changes are common.

Answer 76

b

Question 77

Alternative removal of exons from mRNA is important in which of the following?
a. Troponins and other contractile proteins.
b. Different types of collagen.
c. The disease lupus.
d. Alzheimer’s disease.
e. All of these.

Answer 77

e

Question 78

Capping of eukaryotic mRNA
a. occurs at the 5’ end.
b. occurs at the 3’ end.
c. occurs at both ends.
d. doesn’t occur at all.

Answer 78

a

Question 79

Polyadenylation of eukaryotic mRNA
a. occurs at the 5’ end.
b. occurs at the 3’ end.
c. occurs at both ends.
d. doesn’t occur at all.

Answer 79

b

Question 80

Which of the following is involved in regulation of eukaryotic transcription?
a. Histone acetyltransferase
b. Histone deacetylase
c. Chromatin remodeling complexes
d. Octamer sliding
e. All of the choices

Answer 80

e

Question 81

The combination of events revolving around chromatin remodeling that controls transcription is known as:
a. The genetic code
b. The second genetic code
c. The histone code
d. Histone deacetylase code
e. None of these

Answer 81

c

Question 82

Which of the following is more often associated with transcription being switched off?
a. Presence of histone remodeling complexes SWI/SNF
b. Active Histone Acetyltransferase
c. Unmethylated cytosines
d. Methylated cytosines
e. None of these

Answer 82

d

Question 83

Which of the following RNAs is noted for having a “cloverleaf” structure?
a. mRNA
b. rRNA
c. tRNA
d. All of these

Answer 83

c

Question 84

In eukaryotes, which of the following types of RNA undergo some base modification after polymerization of the
monomers?
a. mRNA
b. tRNA
c. rRNA
d. mRNA and tRNA
e. mRNA and rRNA
f. all of these

Answer 84

f

Question 85

The sequences in eukaryotic DNA known as introns are
a. those included in the final sequence of messenger RNA
b. the intervening sequences not expressed in the final sequence of messenger RNA
c. the binding sites for DNA polymerase
d. the binding sites for RNA polymerase

Answer 85

b

Question 86

A commonly encountered feature of transfer RNA synthesis is
a. the precursor of several tRNA molecules is transcribed in one long polynucleotide sequence
b. there is little or no base modification after transcription
c. modification of the sugar moiety never takes place
d. the covalent binding of tRNA to specific proteins

Answer 86

a

Question 87

Post-transcription processing of mRNA in prokaryotes is required.
a. True
b. False

Answer 87

b

Question 88

The lariat mechanism has been demonstrated by observing the lariat structure using electron microscopy.
a. True
b. False

Answer 88

a

Question 89

Alternative splicing of exons is a mechanism to get more than 1 protein from the same gene.
a. True
b. False

Answer 89

a

Question 90

Which ends of eukaryotic mRNA are protected from degradation?
a. 5’ end only
b. 3’ end only
c. Both ends
d. Neither end
e. The RNA is circular and has no ends.

Answer 90

c

Question 91

Which ends of prokaryotic mRNA are protected from degradation?
a. 5’ end only
b. 3’ end only
c. Both ends
d. Neither end
e. The RNA is circular and has no ends.

Answer 91

d

Question 92

Splicing reactions for exons involve the following mechanisms, except:
a. Small nuclear RNAs
b. Ribozymes
c. Lariat mechanisms
d. Participation of special G residues
e. All of these are involved in splicing reactions

Answer 92

e

Question 93

Ribozymes, the catalytic activity of RNA, were first discovered as part of the snRNA group.
a. True
b. False

Answer 93

a

Question 94

Which category of ribozymes requires an external guanosine frothier action?
a. Group I
b. Group II
c. Both Group I & Group II
d. Neither Group I nor Group II

Answer 94

a

Question 95

Ribozymes
a. are more efficient catalysts than protein-based enzymes.
b. are involved in protein synthesis.
c. always use the same mechanism of catalysis.
d. probably evolved later than protein-based enzymes.

Answer 95

b

Question 96

Which of the following is true about micro RNAs?
a. They are a type of non-coding RNA
b. They are a type of small interfering RNA
c. They have been found only in simple organisms like roundworms
d. All of these are true

Answer 96

a

Question 97

Non-coding RNAs are known to:
a. bind to mRNA targeting them for destruction
b. bind to mRNA preventing their translation
c. promote RNA silencing
d. all of these

Answer 97

d

Question 98

Which of the following is not true about RISC?
a. It is only involved in cleaving dsRNA from viruses
b. It is involved with processing of miRNA and siRNA
c. It uses a protein from the argonaut family
d. It unwinds dsRNA and eventually discards the passenger strand

Answer 98

a

Question 99

In the template DNA strand formed during transcription, the area from the end of the Upstream Promoter (UP)
element to the transcription start site (TSS) is called the _____.
a. proximal promoter
b. core promoter
c. distal promoter
d. extended promoter

Answer 99

d

Question 100

Identify the component of the prokaryotic promoter that is 40 to 60 bases subsequent to the transcription start site and that enhances the binding of RNA polymerase.
a. Core promoter
b. −35 element
c. UP element
d. Pribnow box

Answer 100

c

Question 101

During which phase do the β’- and σ-subunits of RNA polymerase melt 14 base pairs surrounding the transcription
start site, causing the strands to separate?
a. chain initiation
b. chain elongation
c. intrinsic chain termination
d. rho-dependent chain termination

Answer 101

a

Question 102

Identify the part of the RNA polymerase that constitutes the operator and the promoter and modulates the
production of proteins whose amino acid sequence is specified by the structural genes under their control.
a. Transcription start site
b. Termination site
c. Control site
d. Restriction site

Answer 102

c

Question 103

Explain the significance of a structural gene in the synthesis of proteins

Answer 103

A structural gene is a gene that directs the synthesis of a protein under the control of some
regulatory gene. β-Galactosidase is coded for by a structural gene (lacZ). Also, structural genes encode the gene products that are involved in the biochemical pathway of the operon. Two
structural genes—lacY and lacA—form a part of the operon. lacY encodes the enzyme lactose
permease, whereas lacA encodes an enzyme called transacetylase.