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BioChem > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

RNA polymerase:
A) binds tightly to a region of DNA thousands of base pairs away from the DNA to be
transcribed.
B) can synthesize RNA chains without a primer.
C) has a subunit called A (lambda), which acts as a proofreading ribonuclease.
D) separates DNA strands throughout a long region of DNA (up to thousands of base pairs),
then copies one of them.
E) synthesizes RNA chains in the 3’ -> 5’ direction.

A

B) can synthesize RNA chains without a primer.

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2
Q

RNA polymerase from E. coli (core enzyme alone) has all of the following properties except
that it:
A) can extend an RNA chain and initiate a new chain.
B) is required for the synthesis of mRNA, rRNA, and tRNA in E. coli.
C) produces an RNA polymer that begins with a 5’-triphosphate.
D) recognizes specific start signals in DNA.
E) requires all four ribonucleoside triphosphates and a DNA template.

A

D) recognizes specific start signals in DNA.

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3
Q

The sigma factor of E. coli RNA polymerase:
A) associates with the promoter before binding core enzyme.
B) combines with the core enzyme to confer specific binding to a promoter.
C) is inseparable from the core enzyme.
D) is required for termination of an RNA chain.
E) will catalyze synthesis of RNA from both DNA template strands in the absence of the core
enzyme.

A

B) combines with the core enzyme to confer specific binding to a promoter.

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4
Q

Which of the following is not known to be involved in initiation by eukaryotic RNA polymerase II?
A) DNA helicase activity
B) DNA polymerase activity
C) Formation of an open complex
D) Protein binding to specific DNA sequences
E) Protein phosphorylation

A

B) DNA polymerase activity

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5
Q

Which of the following is not a known function of TFIIH?
A) DNA helicase activity.
B) Hydrolysis of ATP.
C) Formation of an open complex
D) Termination of transcription
E) Nucleotide excision repair

A

D) Termination of transcription

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6
Q

The formation of a peptide bond between two amino acids is an example of a(n) ______reaction.

A)cleavage
B)condensation
C)group transfer
D)isomerization
E)oxidation reduction

A

B) condensation

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7
Q

The 5’-terminal cap structure of eukaryotic mRNAs is a(n):
A) 7-methylcytosine joined to the mRNA via a 2’,3’-cyclic linkage.
B) 7-methylguanosine joined to the mRNA via a 5’ -> 3’ diphosphate linkage.
C) 7-methylguanosine joined to the mRNA via a 5’ -> 5’ triphosphate linkage.
D) N6
-methyladenosine joined to the mRNA via a 5’ ->5’ phosphodiester bond.
E) O6
-methylguanosine joined to the mRNA via a 5’ -> 5’ triphosphate linkage.

A

C) 7-methylguanosine joined to the mRNA via a 5’ -> 5’ triphosphate linkage.

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8
Q

Splicing of introns in nuclear mRNA primary transcripts requires:
A) a guanine nucleoside or nucleotide.
B) endoribonucleases.
C) polynucleotide phosphorylase.
D) RNA polymerase II.
E) small nuclear ribonucleoproteins (snRNPs).

A

E) small nuclear ribonucleoproteins (snRNPs).

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9
Q

Which of the following best represents the backbone arrangement of two peptide bonds?
A)Ca—N—Ca—C—Ca—N—Ca—C
B)Ca—N—C—C—N—Ca
C)C—N—Ca—Ca—C—N
D)Ca—C—N—Ca—C—N
E)Ca—Ca—C—N—Ca—Ca—C

A

D)Ca—C—N—Ca—C—N

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10
Q

Differential RNA processing may result in:
A) a shift in the ratio of mRNA produced from two adjacent genes.
B) attachment of the poly(A) tail to the 5’ end of an mRNA.
C) inversion of certain exons in the final mRNA.
D) the production of the same protein from two different genes.
E) the production of two distinct proteins from a single gene.

A

E) the production of two distinct proteins from a single gene.

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11
Q

Which of the following is not part of miRNA formation?
A) Pri-miRNA
B) Pre-miRNA
C) Dicer
D) RISC
E) Pseudouridine

A

E) Pseudouridine

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12
Q

Reverse transcriptase:
A) does not require a primer to initiate synthesis.
B) introduces no errors into genetic material because it synthesizes RNA, not DNA.
C) makes fewer errors in synthesizing a complementary polynucleotide.
D) makes more errors because it lacks the 3’ -> 5’ proofreading exonuclease activity.
E) synthesizes complementary strands in the opposite direction(from 3’ -> 5’.

A

D) makes more errors because it lacks the 3’ -> 5’ proofreading exonuclease activity.

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13
Q

Proteins are linear heteropolymers of
A) a-amino acids
B) B-amino acids
C) R-group
D) L-Alanine
E) Amono group

A

A) a-amino acids

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14
Q

Which of the following is not true about telomerase?
A) Telomerase is a reverse transcriptase.
B) Telomerase utilizes a tRNA template.
C) The primer for telomerase is the 3’-end of the DNA chromosomes.
D) Telomerase synthesizes DNA in the 5’ -> 3’ direction.
E) Telomerase consists of both RNA and protein.

A

B) Telomerase utilizes a tRNA template.

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15
Q

Which of the following are features of the wobble hypothesis?
A) A naturally occurring tRNA exists in yeast that can read both arginine and lysine codons.
B) A tRNA can recognize only one codon.
C) Some tRNAs can recognize codons that specify two different amino acids if both are
nonpolar.
D) The “wobble” occurs only in the first base of the anticodon.
E) The “wobble” occurs only in the third base of the anticodon.

A

D) The “wobble” occurs only in the first base of the anticodon.

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16
Q

Which one of the following is true about the genetic code?
A) All codons recognized by a given tRNA encode different amino acids.
B) It is absolutely identical in all living things.
C) Several different codons may encode the same amino acid.
D) The base in the middle position of the tRNA anticodon sometimes permits “wobble” base
pairing with two or three different codons.
E) The first position of the tRNA anticodon is always adenosine.

A

C) Several different codons may encode the same amino acid.

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17
Q

Which of the following statements about the tRNA that normally accepts phenylalanine is
false? (mRNA codons for phenylalanine are UUU and UUC.)
A) It interacts specifically with the Phe synthetase.
B) It will accept only the amino acid phenylalanine.
C) Its molecular weight is about 25,000.
D) Phenylalanine can be specifically attached to an —OH group at the 3’ end.
E) The tRNA must contain the sequence UUU

A

E) The tRNA must contain the sequence UUU

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18
Q

Which one of the following statements about ribosomes is true?
A) The large subunit contains rRNA molecules; the small subunit does not.
B) The RNA in ribosomes plays a structural, not catalytic, role.
C) There are about 25 ribosomes in an E. coli cell.
D) There are two major ribosomal subunits, each with multiple proteins.
E) Ribosomes are relatively small, with molecular weights less than 10,000.

A

D) There are two major ribosomal subunits, each with multiple proteins.

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19
Q

Cysteine can form what bonds in the cells
A) disulfide bonds
B) hydrophobic bonds
C) covalent bonds
D) hydrogen bonds
E) peptide bonds

A

A) disulfide bonds

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20
Q
  1. It is possible to convert the Cys that is a part of Cys-tRNACys to Ala by a catalytic reduction.
    If the resulting Ala-tRNACys were added to a mixture of (1) ribosomes, (2) all the other tRNAs
    and amino acids, (3) all of the cofactors and enzymes needed to make protein in vitro, and (4)
    mRNA for hemoglobin, where in the newly synthesized hemoglobin would the Ala from Ala-
    tRNACys be incorporated?

A) Nowhere; this is the equivalent of a nonsense mutation.
B) Wherever Ala normally occurs
C) Wherever Cys normally occurs
D) Wherever either Ala or Cys normally occurs
E) Wherever the dipeptide Ala-Cys normally occurs

A

C) Wherever Cys normally occurs

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21
Q

A biochemist is attempting to separate a DNA-binding protein (protein X) from other proteins in a
solution. Only three other proteins (A, B, and C) are present. The proteins have the following
properties:
PI Size Binds to DNA
protein A 7.4 82,000 yes
protein B 3.8 21,500 yes
protein C 7.9 23,000 no
protein X 7.8 22,000 yes

What type of protein separation techniques might she use to separate:

(a) protein X from protein A?
(b) protein X from protein B?
(c) protein X from protein C?

A

(a). Size Exclusion
(b). Ion Exchange
(c). Affinity

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22
Q

T or F (eukaryotic cells): They have three distinct RNA polymerases.

A

True

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23
Q

T or F (eukaryotic cells): Their mRNAs are generally synthesized by RNA polymerase I.

A

False

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24
Q

T or F (eukaryotic cells): RNA polymerase III synthesizes only rRNAs.

A

False

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25
Q

T or F (eukaryotic cells): Their RNA polymerases initiate transcription at specific promoter sites on the DNA

A

True

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26
Q

T or F: Bacterial mRNA is broken down within a few minutes of its formation in E. coli.

A

True

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27
Q

T or F: Bacterial mRNA consists only of the bases that code for amino acids.

A

False

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28
Q

T or F:Bacterial mRNA normally occurs as a double-stranded structure, with one strand
containing codons, the other containing anticodons.

A

False

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29
Q

T or F:Bacterial mRNA can be translated while it is still being synthesized.

A

True

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30
Q

T or F: RNA polymerase: can synthesize RNA chains without a primer.

A

True

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31
Q

T OR F: RNA polymerase from E. coli (core enzyme alone) can recognize specific start signals in DNA.

A

False; It recognize Promoter.

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32
Q

T or F: The sigma factor of E. coli RNA polymerase: combines with the core enzyme to confer specific binding to a primer.

A

False; binding to a promoter.

33
Q

T or F: Termination of transcription is a known function of TFIIH.

A

False
Nucleotide excision repair

34
Q

T or F: Processing of a primary mRNA transcript in a eukaryotic cell normally involve: the conversion of normal bases to modified bases, such as inosine and pseudouridine.

A

False; 5’ cap, 3’ polyA tail, and splice out intron.

35
Q

T or F: The 5’-terminal cap structure of eukaryotic mRNAs is a(n): 7-methylguanosine joined to the mRNA via a 5’ to 5’ triphosphate linkage.

A

True

36
Q

T of F: Compared with DNA polymerase, reverse transcriptase: makes more errors because it lacks the 3’ to 5’ proofreading exonuclease activity.

A

True

37
Q

T of F: Telomerase consists of RNA only.

A

False; RNA and protein.

38
Q

T or F: Several different codons may encode the same amino acid.

A

True

39
Q

T or F: The large subunit of Ribosome contains rRNA molecules; the small subunit does not.

A

False; Both have rRNA

40
Q

5 groupings of amino acid

A

a. Nonpolar (7)
b. Aromatic (3)
c. Polar, uncharged (5)
d. Positively charged (3)
e. Negatively charged (2)

41
Q

T or F- EC have 3 distinct RNA polymerases

A

True

42
Q

GTP

A

Bacterial form of energy

43
Q

T or F- EC mRNAs are generally synthesised by RNA pol I

A

False, its pol II

44
Q

T or F RNA pol III synthesizes only rRNAs

A

False, transcribe variety

45
Q

T or F - EC 5s RNA is synthesized by RNA polymerase I

A

False, synthesized by RNA pol III

46
Q

T or F - EC RNA polymerases initiate transcription at specific promoter sites on DNA

A

True

47
Q

Role of IF-2 in bacterial protein synthesis

A

Brings fMet-tRNA^(fMet) to inittaltion complex bound to GTP

48
Q

Role of Shine Dalgarno/16SRNA in bacterial protein synthesis16S RNA

A

component of the small (30S) subunit of bacterial ribosome. Contains sequence complementary to Shine-Dalgarno sequence in mRNA

49
Q

Role of Peptidyl transferase in bacterial protein synthesis

A

a ribozyme in the 50S ribosomal subunit. Catalyzes the formation of each peptide bond as the ribosome moves along the mRNA

50
Q

Role of Release factors in bacterial protein synthesis

A

proteins that bring about the release of the finished polypeptide when the ribosome encounters a codon in the mRNA

51
Q

Role of elongation factor in bacterial protein synthesis

A

facilitates translocation of the ribosome along the mRNA by promoting the movement of the tRNA-mRNA complex through the ribosome

52
Q

Role of tRNA in bacterial protein synthesis

A

delivers the initiator aa to the ribosome to initiate protein synthesis.

53
Q

Order of components in bacterial protein synthesis (6)

A

IF-2
Shine Dalgarno/16S RNA
Peptidyl transferase
Release factors
Elongation factors
tRNA

54
Q

Principle effect of UV on DNA

A

Covalent bonds between pyrmidine dimers are broken.

55
Q

Describe EF-Tu

A

EF-Tu binds aminoacyl-tRNAs, delivering them to the ribosome for accurate selection and hydrolyzes GTP to ensure peptide bond fo

56
Q

Describe EF-TS

A

·EF-TS: acts as a guanine nuc. exchange factor converting GDP-bound EF-Tu to its active GTP-bound form.

57
Q

Describe EF-G

A

EF-G: Catalyzes ribosome translocation along mRNA during elongation, promoting movement of tRNAs + mRNA

58
Q

mRNA

A

Codes for proteins

59
Q

rRNA

A

components of ribosomes

60
Q

snRNA

A

splicing of RNA transcripts

61
Q

tRNA

A

adapter for protein synthesis

62
Q

How do inhibitors of topoisomerase inhibit the growth of tumors?

A

Dividing cells must replicate their DNA, replication requires the action of topiomerases to resolve DNA tangles, so they would inhibit cancerous cell division

63
Q

Why does lowering ionic strength of a solution of a double-stranded DNA permit the DNA to denature more readily?

A

Reduces screen affects of ions which decraeses elctrostatic interactions between negative hospate groups in DNA, which facilitates DNA denaturation at lower temps)

64
Q

Protein X from A

A

Size exclusiion bc simalir pI values

65
Q

Protein X from B

A

Ion exchange bc totally different pI values

66
Q

Protein X from C

A

Affinity chromatography

67
Q

T or F - In eukaryotes, the 3’ end of the mRNA is associated w/ the 5’ end during initiation

A

True

68
Q

T or F - In prokaryotes, it initiated at an AUG near a Shine-Dalagmo sequence in the mRNA

A

False, that’s in eukaryotes

69
Q

T or F - In prokaryotes, its initiated with MET whereas in eukaryotes, its fMET

A

False, reverse that

70
Q

T or F - In prokaryotes, translation + transcription are coupled, but in eukaryotes, it’s not.

A

True

71
Q

Processing of a primary mRNA transcript in a eukaryotic cell does not normally involve:
a) attachment of a long polA sequence at the 3’ end
b) conversation of moral bases to modified bases, suck as inosine and pseudouridine
c) excision of intervening sequences
d) joining exons
e) methylation of one or more guanine nucleotides at 5’ end

A

b) conversation of moral bases to modified bases, suck as inosine and pseudouridine

72
Q

Which of the following is not usually essential for the catalytic activity of ribozymes?
a) correct base pairing
b) correct base sequence
c) correct interaction w/ protein
d) correct secondary structure
e) correct 3-d structure

A

c) correct interaction w/ protein

73
Q

Compared w/ DNA polymerase, reverse transcriptase:
a) Does not require a primer to initiate transcriptase
b) introduces no errors into genetic materials bc it synthesizes RNA, not DNA
c) makes fewer errors in synthesizing complementary polynucleotide
d) makes more errors as it lacks the 3’->5’ proofreading exonuclease activity
e) synthesizes complementary strands in the opposite direction from 3’->5’

A

d) makes more errors as it lacks the 3’->5’ proofreading exonuclease activity

74
Q

AZT used to treat HIV, acts in HIV-infected cells by
a) blocking ATP production
b) blocking deoxynucleotide synthesis
c) inhibiting reverse transcriptase
d) inhibiting RNA polymerase II
e) inhibiting RNA processing

A

c) inhibiting reverse transcriptase

75
Q

Aminoacyl-tRNA synthetases aa activating enzymes
a) recognize specific tRNA molecules and specific amino acids
b) in conjunction with another enzyme attach the amino acid to the tRNA
c) interact directly w/ free ribosomes
d) occur in multiple forms for each amino acid
e) require GTP to active amino acid

A

b) in conjunction with another enzyme attach the amino acid to the tRNA

76
Q

Which of the following states about the elongation phase of protein synthesis is true?
A) At least five high-energy phosphoryl groups are expended for each peptide bond formed
B) During elongation, incoming aminoacylated tRNAs are first bound in the P site. C) Elongation factor EF-Tu facilitates translocation.
D) Peptidyl transferase catalyzes the attack of the carboxyl group of the incoming amino acid on an ester linkage in the nascent polypeptide.
E) Peptidyl transferase is a ribozyme.

A

E) Peptidyl transferase is a ribozyme.

77
Q

At the isoelectric pH of a tetrapeptide:
A) only the amino and carboxyl termini contribute charge.
B) the amino and carboxyl termini are not charged.
C) the total net charge is zero.
D) there are four ionic charges.
E) two internal amino acids of the tetrapeptide cannot have ionizable R groups.

A

C) the total net charge is zero.

78
Q

In a conjugated protein, a prosthetic group
A) fibrous region of a globular protein.
B) a nonidentical subunit of a protein with many identical subunits.
C) a part of the protein that
is not composed of amino acids.
D) a subunit of an oligomeric protein.
E) synonymous with “protomer.”

A

C) a part of the protein that
is not composed of amino acids.

BioChem (5 decks)

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