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SAC Microbiology > Lecture 7 > Flashcards

Lecture 7 Flashcards

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1
Q

Opens the DNA helix by breaking hydrogen bonds between the nitrogenous bases

A

Helicase

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2
Q

Seals the gaps between the Okazaki fragments on the lagging strand to create one continuous DNA strand

A

Ligase

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3
Q

Synthesizes RNA primers needed to start replication

A

Primase

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4
Q

RNA polymerase binds to DNA at a sequence called a ____ during the initiation of transcription.

A

Promoter

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5
Q

During DNA replication:

A) both leading and lagging daughter DNA strands are synthesized in the 5’ to 3’ direction.
B) both leading and lagging daughter DNA strands are synthesized in the 3’ to 5’ direction.
C) the leading strand is synthesized in the 5’ to 3’ direction but the lagging strand is synthesized 3’ to 5’.
D) the leading strand is synthesized in the 3’ to 5’ direction but the lagging strand is synthesized 5’ to 3’.

A

A) both leading and lagging daughter DNA strands are synthesized in the 5’ to 3’ direction.

DNA polymerases can only add new nucleotides onto a free 3’ OH, so DNA synthesis always occurs in a 5’ to 3’ direction (every newly made strand starts with a 5’ triphosphate and ends with a 3’ OH). Since DNA is antiparallel at each replication fork, there is both a leading and a lagging strand.

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6
Q

Gene expression changes caused by use of an alternative sigma factor represent what level of gene regulation?

A) changing the DNA sequence
B) transcriptional control
C) translational control
D) post-translational control

A

B) transcriptional control

Sigma factor is involved in the transcription of prokaryotes

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7
Q

Sigma protein is involved in ?

A) initiation of transcription
B) elongation of transcription
C) initiation of translation
D) elongation of translation

A

A) initiation of transcription

Sigma factor is involved in the initiation of transcription in prokaryotes

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8
Q

Which of the following is true of mutations?

A) They always cause a change to an organism’s genotype
B) They always cause a change to an organism’s phenotype
C) They are always harmful for the organism
D) They are always fixed by DNA repair enzymes

A

A) They always cause a change to an organism’s genotype

In mutation, nucleotide base change, hence change in genotype

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9
Q

Which of the following is true of transcription and translation in bacteria?

A) Translation starts after transcription ends, and both processes occur in the nucleus
B) Translation starts after transcription ends, and both processes occur in the cytoplasm
C) Translation starts before transcription ends, and both processes occur in the nucleus
D) Translation starts before transcription ends, and both processes occur in the cytoplasm

A

D) Translation starts before transcription ends, and both processes occur in the cytoplasm

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10
Q

At the end of translation initiation in bacteria:

A) the fMet tRNA is in the A site of the 70S ribosome
B) the fMet tRNA is in the P site of the 70S ribosome
C) RNA polymerase has escaped the promoter, leaving sigma behind
D) the fMet tRNA is in the A site of the 30S subunit but the 50S subunit is not yet present

A

B) the fMet tRNA is in the P site of the 70S ribosome

Because the first amino acid bearing tRNA i.e. fMet tRNA enters at P site of ribosomes. All other tRNA enters at A site of ribosomes

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11
Q

Which type of protein is likely to be secreted out of the cell through membrane export complexes?

A) a ribosomal protein
B) a sigma factor
C) an aminoacyl-tRNA synthetase
D) a toxin

A

D) a toxin

Toxin is released outside because it helps the bacteria to protect themselves from other foreign body.

Sigma factor, ribosomal protein, and amino acyl tRNA synthetase are required by the cell in RNA polymerase, ribosome formation, and linking of amino acid to tRNA respectively. That’s why they are not expelled outside.

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12
Q

If the human insulin gene (as found in the human genome) was transformed into Escherichia coli, why wouldn’t E. coli produce functional insulin protein?

A) because human proteins can only be produced in humans
B) because E. coli lack insulin receptors that could bind the finished product
C) because the genetic code differs between humans and E. coli
D) because E. coli do not have the machinery to splice introns out of the mRNA

A

D) because E. coli do not have the machinery to splice introns out of the mRNA

Because splicing process is not found in prokaryotes. The removal of intron is not found in prokaryotes.

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13
Q

Bacterial chromosomes are:

A) rarely circular
B) never circular
C) always circular
D) usually circular

A

D) usually circular

Bacterial chromosomes are usually circular, but may be linear or even a mix of linear and circular chromosomes.

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14
Q

This enzyme adds negative supercoils to the DNA to reduce the strain on the DNA

A

Gyrase

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15
Q

This enzyme forms a covalent bond in the phosphodiester backbone of DNA

A

DNA Ligase

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16
Q

This enzyme complex adds nucleotides to both leading and lagging strands to generate new copies of DNA

A

DNA polymerase

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17
Q

This enzyme unwinds DNA to create a replication fork

A

Helicase

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18
Q

____ is part of the RNA polymerase holoenzyme and is responsible for binding the promoter during transcription initiation.

A

Sigma protein

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19
Q

During translational initiation, the fMet tRNA binds into the ___ site and the 30S and 50S ribosomal subunits join to form the ___ complex.

A

P; 70S

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20
Q

The anticodon is part of ____.

A) tRNA
B) mRNA
C) the 30S subunit of the ribosome
D) aminoacyl-tRNA synthetase

A

A) tRNA

Anticodons present in tRNAs bind to codons in mRNAs.

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21
Q

The____ deliver the correct amino acid to the ribosome based on codon-anticodon base pairing.

A

tRNA’s

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22
Q

What is the start codon?

A

AUG

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23
Q

Class of enzymes that adds nucleotides to the free 3’-OH group of a growing DNA chain that are complementary to the template strand.

A

DNA polymerase

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24
Q

Enzyme that unwinds DNA by breaking the hydrogen bonds between the nitrogenous base pairs, using ATP

A

Helicase

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25
Q

Enzyme responsible for facilitating topological transitions of DNA, relaxing it from its supercoiled state

A

DNA gyrase

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26
Q

Short complementary sequence of five to 10 RNA nucleotides synthesized on the template strand by primase that provides a free 3’-OH group to which DNA polymerase can add DNA nucleotides

A

Primer

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27
Q

This is needed to transport amino acids to the ribosomes to synthesize proteins

A

Transfer RNA (tRNA)

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28
Q

This carries genetic information from DNA into the cytoplasm to ribosomes, where amino acids are arranged and proteins are made.

A

Messenger RNA (mRNA)

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29
Q

RNA polymerase enzyme that synthesizes the RNA primer required to initiate DNA synthesis

A

Primase

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30
Q

What synthesizes RNA primers needed to start replication?

A

Primase

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31
Q

Which of the following enzymes is responsible for adding deoxyribonucleotides to a growing nucleotide strand during DNA replication?

A. Polymerase
B. Ligase
C. Primase
D. Helicase

A

Polymerase

32
Q

All types of RNA are created during a process called ____ , but only one kind is interpreted as codons by the ribosome to make a protein.

A

Transcription

33
Q

Which type of RNA is used as a template for protein synthesis?

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

A

mRNA

34
Q

Why are bacterial plasmids problematic for human health?

A. They can integrate into the human nuclear genome.
B. They can be manipulated in laboratories.
C. They are circular.
D. They can transfer across species.

A

D. They can transfer across species.

35
Q

DNA synthesis can be described as:

A. semiconservative.
B. perfect.
C. conservative.
D. disruptive.

A

A. semiconservative.

36
Q

During DNA replication:

A. both leading and lagging daughter DNA strands are synthesized in the 3′ to 5′ direction.
B. the leading strand is synthesized in the 5′ to 3′ direction but the lagging strand is synthesized 3′ to 5′.
C.both leading and lagging daughter DNA strands are synthesized in the 5′ to 3′ direction.
D. the leading strand is synthesized in the 3′ to 5′ direction but the lagging strand is synthesized 5′ to 3′.

A

C.both leading and lagging daughter DNA strands are synthesized in the 5′ to 3′ direction.

37
Q 
The production of RNA complementary to a DNA template is known as\_\_\_\_\_\_\_\_.
A. translation
B. transcription
C. reverse transcription
D. replication
A

B. transcription

38
Q 
Sigma protein is involved in \_\_\_\_\_\_\_\_.
A. elongation of transcription
B. elongation of translation
C. initiation of translation
D. initiation of transcription
A

D. initiation of transcription

39
Q

If the human insulin gene (as found in the human genome) was transformed into Escherichia coli, why wouldn’t E. coli produce functional insulin protein?

A. because the genetic code differs between humans and E. coli
B. because E. coli lack insulin receptors that could bind the finished product
C. because human proteins can only be produced in humans
D. because E. coli do not have the machinery to splice introns out of the mRNA

A

D. because E. coli do not have the machinery to splice introns out of the mRNA

40
Q 
In bacteria, translation starts \_\_\_\_\_\_\_\_ transcription ends, and both processes occur in the \_\_\_\_\_\_\_\_.
A. before; nucleus
B. after; cytoplasm
C. after; nucleus
D. before; cytoplasm
A

D. before; cytoplasm

41
Q

At the end of translation initiation in bacteria:

A. The fMet tRNA is in the P site of the 70S ribosome.
B. The fMet tRNA is in the A site of the 30S subunit but the 50S subunit is not yet present.
C. The fMet tRNA is in the A site of the 70S ribosome.
D. RNA polymerase has escaped the promoter, leaving sigma behind.

A

A. The fMet tRNA is in the P site of the 70S ribosome.

42
Q

The anticodon is part of:

A. aminoacyl-tRNA synthetase.
B. mRNA.
C. tRNA.
D. the 30S subunit of the ribosome.

A

C. tRNA.

43
Q

The RNA polymerase enzyme, when creating mRNA, acts in a manner very similar to DNA polymerase when the DNA polymerase copies DNA. RNA polymerase will add nucleotides to a growing RNA chain. The only difference is that the RNA polymerase must complex with another protein to initiate RNA synthesis. What is the name of this other protein?

A. alpha factor
B. sigma factor
C. beta factor
D. omega factor

A

B. sigma factor

44
Q

Which aspect of bacterial genome structure is the same in eukaryotes ?

A. The genome is composed of double helical DNA.
B. Genes are often arranged in tandem, within an operon.
C. The genome is compact, with genes interspersed by relatively short noncoding sequences .
D. Most genomes are circular.

A

A. The genome is composed of double helical DNA.

45
Q

The leading and the lagging strands differ in that
A) the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
B) the leading strand is synthesized by adding nucleotides to the 3’ end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5’ end.
C) the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.
D) both A and B
E) both A and C

A

E) both A and C

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

the leading strand is synthesized continuously, whereas the lagging strand is synthesized in short fragments that are ultimately stitched together.

46
Q

What kind of molecule or substance is the primer that is used to initiate the synthesis of a new DNA strand?

A) RNA
B) DNA
C) protein
D) phosphate
E) sulfur
A

A) RNA

47
Q

What is the function of DNA polymerase?

A) to unwind the DNA helix during replication
B) to seal together the broken ends of DNA strands
C) to add nucleotides to the end of a growing DNA strand
D) to degrade damaged DNA molecules
E) to rejoin the two DNA strands (one new and one old) after replication

A

C) to add nucleotides to the end of a growing DNA strand

48
Q

What determines the nucleotide sequence of the newly synthesized strand during DNA replication?

A) the particular DNA polymerase catalyzing the reaction
B) the relative amounts of the four nucleoside triphosphates in the cell
C) the nucleotide sequence of the template strand
D) the primase used in the reaction
E) both A and D

A

D) the primase used in the reaction

49
Q

Which enzyme catalyzes the elongation of a DNA strand in the 5’ 3’ direction?

A) primase
B) DNA ligase
C) DNA polymerase
D) topoisomerase
E) helicase
A

C) DNA polymerase

50
Q

The strands that make up DNA are antiparallel. This means that:

A) the twisting nature of DNA creates nonparallel strands.
B) the 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.
C) base pairings create unequal spacing between the two DNA strands.
D) one strand is positively charged and the other is negatively charged.
E) one strand contains only purines and the other contains only pyrimidines.

A

B) the 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.

51
Q

What kind of chemical bond is found between paired bases of the DNA double helix?

A) hydrogen
B) ionic
C) covalent
D) sulfhydryl
E) phosphate
A

A) hydrogen

52
Q

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

A) synthesize RNA nucleotides to make a primer
B) catalyze the lengthening of telomeres
C) join Okazaki fragments together
D) unwind the parental double helix
E) stabilize the unwound parental DNA
A

C) join Okazaki fragments together

53
Q

During the replication of DNA, ____.

a. Both strands of a molecule act as templates
b. the cell undergoes mitosis
c. only one strand of the molecule acts as a template
d. errors never occur
e. the reaction is catalyzed by RNA polymerase

A

a. Both strands of a molecule act as templates

54
Q

In bacteria, the initiation of replication occurs
at the origin of replication, where supercoiled
DNA is unwound by ____, made singlestranded
by ____, and bound by singlestranded
binding protein to maintain its
single-stranded state.

A

DNA gyrase; helicase

55
Q

During elongation, the ____ of DNA is

synthesized continuously from a single primer.

A

leading strand

56
Q

The ____ is synthesized

discontinuously in short Okazaki fragments.

A

lagging strand

57
Q

RNA polymerase binds to DNA at a sequence
called a ____ during the initiation of
transcription.

A

promoter

58
Q

In _____, polypeptides are synthesized using mRNA sequences and cellular machinery, including tRNA that match mRNA codons to specific amino acids

A

translation

59
Q

Gene expression in prokaryotes is largely

regulated at the ?

A

point of transcription

60
Q

According to the central dogma, which of the following represents the flow of genetic information in cells?

A. protein to DNA to RNA
B. DNA to RNA to protein
C. RNA to DNA to protein
D. DNA to protein to RNA

A

B. DNA to RNA to protein

61
Q

Which of the following is the enzyme that
replaces the RNA nucleotides in a primer with
DNA nucleotides?

A. DNA polymerase III
B. DNA polymerase I
C. primase
D. helicase

A

B. DNA polymerase I

62
Q

Which of the following is not involved in the
initiation of replication?

A. ligase
B. DNA gyrase
C. single-stranded binding protein
D. primase

A

A. ligase

63
Q

Which of the following enzymes involved in DNA
replication is unique to eukaryotes?

A. helicase
B. DNA polymerase
C. ligase
D. telomerase

A

D. telomerase

64
Q

Which of the following would be synthesized using 5′-CAGTTCGGA-3′ as a template?

A. 3′-AGGCTTGAC-4′
B. 3′-TCCGAACTG-5′
C. 3′-GTCAAGCCT-5′
D. 3′-CAGTTCGGA-5′

A

C. 3′-GTCAAGCCT-5′

65
Q

During which stage of bacterial transcription is the σ subunit of the RNA polymerase involved?

A. initiation
B. elongation
C. termination
D. splicing

A

A. initiation

66
Q

Which of the following components is involved in
the initiation of transcription?

A. primer
B. origin
C. promoter
D. start codon

A

C. promoter

67
Q

Which of the following is the name of the three-base
sequence in the mRNA that binds to a
tRNA molecule?

A. P site
B. codon
C. anticodon
D. CCA binding site

A

B. codon

68
Q

Which is the mechanism by which improper excision of a prophage from a bacterial chromosome result in packaging of bacterial genes near the integration site into a phage head?

A. conjugation
B. generalized transduction
C. specialized transduction
D. transformation

A

C. specialized transduction

69
Q

Which of the following refers to the uptake of naked DNA from the surrounding environment?

A. conjugation
B. generalized transduction
C. specialized transduction
D. transformation

A

D. transformation

70
Q

The F plasmid is involved in which of the following processes?

A. conjugation
B. transduction
C. transposition
D. transformation

A

A. conjugation

71
Q

Which of the following refers to the mechanism of horizontal gene transfer naturally responsible for the spread of antibiotic resistance genes within a bacterial population?

A. conjugation
B. generalized transduction
C. specialized transduction
D. transformation

A

A. conjugation

72
Q

An operon of genes encoding enzymes in a
biosynthetic pathway is likely to be which of the
following?

A. inducible
B. repressible
C. constitutive
D. monocistronic

A

B. repressible

73
Q

An operon encoding genes that are transcribed
and translated continuously to provide the cell
with constant intermediate levels of the protein
products is said to be which of the following?

A. repressible
B. inducible
C. constitutive
D. activated

A

C. constitutive

74
Q

Which of the following conditions leads to
maximal expression of the lac operon?

A. lactose present, glucose absent
B. lactose present, glucose present
C. lactose absent, glucose absent
D. lactose absent, glucose present

A

A. lactose present, glucose absent

75
Q

Naked DNA is taken up from the environment

A

Transformation

76
Q

Genes are transferred between cells in a virus

A

Transduction

77
Q

Use of a hollow tube called a conjugation pilus to transfer genes between cells

A

Conjugation

SAC Microbiology (19 decks)

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