Final Exam Review

Question 1

Which of the following deoxyoligonucleotides will hybridize with a DNA containing the
sequence (5’)AGACTGGTC(3’)?

A) (5’)CTCATTGAG(3’)
B) (5’)GACCAGTCT(3’)
C) (5’)GAGTCAACT(3’)
D) (5’)TCTGACCAG(3’)
E) (5’)TCTGGATCT(3’)

Answer 1

B) (5’)GACCAGTCT(3’)

Question 2

The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA:
A) always link A with T and G with C.
B) are susceptible to alkaline hydrolysis.
C) are uncharged at neutral pH.
D) form between the planar rings of adjacent bases.
E) join the 3’ hydroxyl of one nucleotide to the 5’ Phosphate of the next.

Answer 2

E) join the 3’ hydroxyl of one nucleotide to the 5’ Phosphate of the next.

Question 3

Chargaff’s rules state that in typical DNA:
A) A = G.
B) A = C.
C) A = U.
D) A + T = G + C.
E) A + G = T + C.

Answer 3

E) A + G = T + C.

Question 4

B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å
per base pair.
A) left; 20; 3.9
B) right; 18; 3.4
C) right; 18; 3.6
D) right; 20; 3.4
E) right; 23; 2.6

Answer 4

D) right; 20; 3.4

Question 5

In living cells, nucleotides and their derivatives can serve as:
A) carriers of metabolic energy.
B) enzyme cofactors.
C) intracellular signals.
D) precursors for nucleic acid synthesis.
E) All of the above.

Answer 5

E) All of the above.

Question 6

The most precise modern definition of a gene is a segment of genetic material that:
A) codes for one polypeptide.
B) codes for one polypeptide or RNA product.
C) determines one phenotype.
D) determines one trait.
E) codes for one protein.

Answer 6

B) codes for one polypeptide or RNA product.

Question 7

Introns:
A) are frequently present in prokaryotic genes but are rare in eukaryotic genes.
B) are spliced out before transcription.
C) are translated but not transcribed.
D) can occur many times within a single gene.
E) encode unusual amino acids in proteins

Answer 7

D) can occur many times within a single gene

Question 8

The DNA in a bacterial (prokaryotic) chromosome is best described as:
A) a single circular double-helical molecule.
B) a single linear double-helical molecule.
C) a single linear single-stranded molecule.
D) multiple linear double-helical molecules.
E) multiple linear single-stranded molecules

Answer 8

A) a single circular double-helical molecule.

Question 9

The DNA in a eukaryotic chromosome is best described as:
A) a single circular double-helical molecule.
B) a single linear double-helical molecule.
C) a single linear single-stranded molecule.
D) multiple linear double-helical molecules.
E) multiple linear single-stranded molecules

Answer 9

B) a single linear double-helical molecule.

Question 10

Which of the following does not contribute to the octameric histone core?
A) H1
B) H2A
C) H2B
D) H3
E) H4

Answer 10

A) H1

Question 11

The fundamental repeating unit of organization in a eukaryotic chromosome is the:
A) centrosome.
B) lysosome.
C) microsome.
D) nucleosome.
E) polysome.

Answer 11

D) nucleosome.

Question 12

When a DNA molecule is described as replicating bidirectionally, that means that it has two:
A) chains.
B) independently replicating segment.
C) origins.
D) replication forks.
E) termination points

Answer 12

D) replication forks.

Question 13

The fundamental repeating unit of organization in a eukaryotic chromosome is the:
A) centrosome.
B) lysosome.
C) microsome.
D) nucleosome.
E) polysome

Answer 13

D) nucleosome

Question 14

An Okazaki fragment is a:
A) fragment of DNA resulting from endonuclease action.
B) fragment of RNA that is a subunit of the 30S ribosome.
C) piece of DNA that is synthesized in the 3’ Æ 5’ direction.
D) segment of DNA that is an intermediate in the synthesis of the lagging strand.
E) segment of mRNA synthesized by RNA polymerase.

Answer 14

D) segment of DNA that is an intermediate in the synthesis of the lagging strand.

Question 15

Prokaryotic DNA polymerase III:
A) contains a 5’ -> 3’ proofreading activity to improve the fidelity of replication.
B) does not require a primer molecule to initiate replication.
C) has a b subunit that acts as a circular clamp to improve the processivity of DNA synthesis.
D) synthesizes DNA in the 3’ -> 5’ direction.
E) synthesizes only the leading strand; DNA polymerase I synthesizes the lagging strand

Answer 15

C) has a b subunit that acts as a circular clamp to improve the processivity of DNA synthesis.

Question 16

In contrast to bacteria, eukaryotic chromosomes need multiple DNA replication origins
because:
A) eukaryotic chromosomes cannot usually replicate bidirectionally.
B) eukaryotic genomes are not usually circular, like the bacterial chromosome is.
C) the processivity of the eukaryotic DNA polymerase is much less than the bacterial enzyme.
D) their replication rate is much slower, and it would take too long with only a single origin per
chromosome.
E) they have a variety of DNA polymerases for different purposes, and need a corresponding
variety of replication origins

Answer 16

D) their replication rate is much slower, and it would take too long with only a single origin per
chromosome.

Question 17

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E.
coli?
A) DNA glycosylase
B) DNA helicase II
C) DNA ligase
D) DNA polymerase III
E) Exonuclease I

Answer 17

A) DNA glycosylase

Question 18

The ABC excinuclease is essential in:
A) base-excision repair.
B) methyl-directed repair.
C) mismatch repair.
D) nucleotide-excision repair.
E) SOS repair.

Answer 18

D) nucleotide-excision repair.

Question 19

In homologous genetic recombination, RecA protein is involved in:
A) Strand invasion to form a Holliday intermediates.
B) introduction of negative supercoils into the recombination products.
C) nicking the two duplex DNA molecules to initiate the reaction.
D) pairing a DNA strand from one duplex DNA molecule with sequences in another duplex,
regardless of complementarity.
E) resolution of the Holliday intermediate.

Answer 19

A) Strand invasion to form a Holliday intermediates.

Question 20

A lack of ascorbic acid (vitamin C) will result in reduced stability of: A) keratin.
B) collagen.
C) fibronin.
D) myoglobin.
E) None of the answers are correct.

Answer 20

B) collagen.

Question 21

Which method would be MOST useful to solve the structure of a small, soluble protein that does not easily form a repeating structure (crystal)?
A) NMR
B) x-ray crystallography C) mass spectrometry D) circular dichroism
E) electron microscopy

Answer 21

A) NMR

Question 22

Which disease is NOT one characterized by or associated with an unfolded protein aggregate? A) Alzheimer disease
B) diabetes
C) Parkinson disease
D) scurvy
E) All of these diseases are linked to unfolded protein aggregates.

Answer 22

D) scurvy

Question 23

When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by:
A) one O atom and one amino acid atom.
B) one O2 molecule and one amino acid atom.
C) one O2 molecule and one heme atom. D) two O atoms.
E) two O2 molecules.

Answer 23

B) one O2 molecule and one amino acid atom.

Question 24

Which statement about protein-ligand binding is CORRECT?
A) The Ka is equal to the concentration of ligand when all of the binding sites are occupied. B) The Ka is independent of such conditions as salt concentration and pH.
C) The larger the Ka (association constant), the weaker the affinity.
D) The larger the Ka, the faster is the binding.
E) The larger the Ka, the smaller the Kd (dissociation constant)

Answer 24

E) The larger the Ka, the smaller the Kd (dissociation constant)

Question 24

In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by:
B) one O2
molecule and one amino acid atom.
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A) Fe2+ binding.
B) heme binding.
C) oxygen binding.
D) subunit association. E) subunit dissociation

Answer 24

C) oxygen binding.

Question 25

Carbon monoxide (CO) is toxic to humans because it:
A) binds to myoglobin and causes it to denature.
B) is rapidly converted to toxic CO2.
C) binds to the globin portion of hemoglobin and prevents the binding of O2.
D) binds to the Fe in hemoglobin and prevents the binding of O2.
E) binds to the heme portion of hemoglobin and causes heme to unbind from hemoglobin.

Answer 25

D) binds to the Fe in hemoglobin and prevents the binding of O2.

Question 25

Which statement is NOT correct concerning 2,3-bisphosphoglycerate (BPG)? A) It binds at a distance from the heme groups of hemoglobin.
B) It binds with lower affinity to fetal hemoglobin than to adult hemoglobin.
C) It increases the affinity of hemoglobin for oxygen.
D) It is an allosteric modulator.
E) It is normally found associated with the hemoglobin extracted from red blood cells

Answer 25

C) It increases the affinity of hemoglobin for oxygen.

Question 26

Which pair of amino acids can be used to measure the concentration of proteins based on absorption of UV light?
A) proline and valine
B) serine and threonine
C) aspartate and glutamate D) lysine and histidine
E) tyrosine and tryptophan

Answer 26

E) tyrosine and tryptophan

Question 26

wo proteins bind to the same ligand, and protein A has half of its binding sites occupied when the ligand concentration is 0.5 mM, while protein B has half of its binding sites occupied when the ligand concentration is at 0.3 mM. Which protein binds the ligand more strongly, and what is the dissociation constant for that protein-ligand interaction?
A) Protein A binds more strongly, and Kd = 0.3 mM.
B) Protein A binds more strongly, and Kd = 0.5 mM.
C) Protein B binds more strongly, and Kd = 0.3 mM.
D) Protein B binds more strongly, and Kd = 0.5 mM.
E) Both proteins bind the ligand with the same affinity, and Kd = 0.4 mM

Answer 26

C) Protein B binds more strongly, and Kd = 0.3 mM.

Question 27

Muscle fibers are made up of which protein? A) myosin
B) actin
C) calcitonin
D) both myosin and actin
E) both myosin and calcitonin

Answer 27

D) both myosin and actin

Question 28

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  (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.

Answer 28

B) can synthesize RNA chains without a primer.

Question 29

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

Answer 29

D) Termination of transcription

Question 30

Processing of a primary mRNA transcript in a eukaryotic cell does not normally involve:
A) attachment of a long poly(A) sequence at the 3’ end.
B) conversion of normal bases to modified bases, such as inosine and pseudouridine.
C) excision of intervening sequences (introns).
D) joining of exons.
E) methylation of one or more guanine nucleotides at the 5’ end.

Answer 30

B) conversion of normal bases to modified bases, such as inosine and pseudouridine.

Question 31

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)

Answer 31

E) small nuclear ribonucleoproteins (snRNPs)

Question 32

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.

Answer 32

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

Question 33

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

Answer 33

E) Pseudouridine

Question 34

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 with protein
D) Correct secondary structure
E) Correct three-dimensional structure

Answer 34

C) Correct interaction with protein

Question 35

Compared with DNA polymerase, 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’

Answer 35

D) makes more errors because it lacks the 3’  5’ proofreading exonuclease activity

Question 36

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.

Answer 36

B) Telomerase utilizes a tRNA template.

Question 37

Which of these enzymes is not directly involved in methyl-directed mismatch repair in E. coli?
A) DNA glycosylase
B) DNA helicase II
C) DNA ligase
D) DNA polymerase III
E) Exonuclease I

Answer 37

A) DNA glycosylase

Question 38

In baIn base-excision repair, the first enzyme to act is:
A) AP endonuclease.
B) Dam methylase. C) DNA glycosylase. D) DNA ligase.
E) DNA polymerase.se-excision repair, the first enzyme to act is:
A) AP endonuclease.
B) Dam methylase. C) DNA glycosylase. D) DNA ligase.
E) DNA polymerase.

Answer 38

A) AP endonuclease.

Question 39

An alternative repair system by error-prone translesion DNA synthesis can result in a high mutation rate, because:
A) alternative modified nucleotides can be incorporated more readily.
B) interference from the RecA and SSB proteins hinders the normal replication accuracy.
C) replication proceeds much faster than normal, resulting in many more mistakes.
D) the DNA polymerases involved cannot facilitate base-pairing as well as DNA polymerase III.
E) the DNA polymerases involved lack exonuclease proofreading activities.

Answer 39

E) the DNA polymerases involved lack exonuclease proofreading activities.

Question 40

In homologous recombination in E. coli, the protein that moves along a double-stranded DNA, unwinding the strands ahead of it and degrading them, is:
A) chi.
B) DNA ligase.
C) RecA protein.
D) RecBCD enzyme.
E) RuvC protein (resolvase).

Answer 40

D) RecBCD enzyme.

Question 41

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.

Answer 41

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

Question 42

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.

Answer 42

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

Question 43

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.

Answer 43

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

Question 44

Aminoacyl-tRNA synthetases (amino acid 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 with free ribosomes.
D) occur in multiple forms for each amino acid.
E) require GTP to activate the amino acid.

Answer 44

A) “recognize” specific tRNA molecules and specific amino acids.

Question 45

The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA: A) always link A with T and G with C.
B) are susceptible to alkaline hydrolysis.
C) are uncharged at neutral pH.
D) form between the planar rings of adjacent bases.
E) join the 3’ hydroxyl of one nucleotide to the 5’ hydroxyl of the next

Answer 45

E) join the 3’ hydroxyl of one nucleotide to the 5’ hydroxyl of the next

Question 46

In the Watson-Crick model of DNA structure:
A) both strands run in the same direction, 3’ 5’; they are parallel.
B) phosphate groups project toward the middle of the helix, where they are protected from
interaction with water.
C) T can form three hydrogen bonds with either G or C in the opposite strand.
D) the distance between the sugar backbone of the two strands is just large enough to
accommodate either two purines or two pyrimidines.
E) the distance between two adjacent bases in one strand is about 3.4 Å.

Answer 46

E) the distance between two adjacent bases in one strand is about 3.4 Å.

Question 47

In the Watson-Crick model for the DNA double helix, which of the following is not true? A) The two strands run anti-parallel to one another.
B) The base-pairing occurs on the inside of the double helix.
C) The double helix is right-handed.
D) There are two equally sized grooves that run up the sides of the helix. E) The two strands have complementary sequences.

Answer 47

C) The double helix is right-handed.

Question 48

Which of the following is not true of all naturally occurring DNA? A) Deoxyribose units are connected by 3’,5’-phosphodiester bonds. B) The amount of A always equals the amount of T.
C) The ratio A+T/G+C is constant for all natural DNAs.
D) The two complementary strands are antiparallel. E) Two hydrogen bonds form between A and T.

Answer 48

C) The ratio A+T/G+C is constant for all natural DNAs.

Question 49

The linking number (Lk) of a closed-circular, double-stranded DNA molecule is changed by: A) breaking a strand, then rejoining it.
B) breaking a strand, unwinding or rewinding the DNA, then rejoining it.
C) breaking all hydrogen bonds in the DNA.
D) supercoiling without the breaking of any phosphodiester bonds. E) underwinding without the breaking of any phosphodiester bonds.

Answer 49

B) breaking a strand, unwinding or rewinding the DNA, then rejoining it.

Question 49

The DNA in a eukaryotic chromosome is best described as:
A) a single circular double-helical molecule.
B) a single linear double-helical molecule.
C) a single linear single-stranded molecule.
D) multiple linear double-helical molecules.
E) multiple linear single-stranded molecules.

Answer 49

B) a single linear double-helical molecule.

Question 50

Introns:
A) are frequently present in prokaryotic genes but are rare in eukaryotic genes. B) are spliced out before transcription.
C) are translated but not transcribed.
D) can occur many times within a single gene.
E) encode unusual amino acids in proteins.

Answer 50

D) can occur many times within a single gene.`

Question 51

It is correct to say that DNA supercoiling cannot: A) be induced by strand separation.
B) be induced by underwinding of the double helix. C) form if there is Z-DNA structure present.
D) occur if a closed circular double-stranded DNA molecule has a nick.
E) result in compaction of the DNA structure.

Answer 51

D) occur if a closed circular double-stranded DNA molecule has a nick.`

Question 52

The Km for this enzyme is approximately:
a) 1mM.
b) 1000 mM.
c) 2mM.
d) 4mM.
e) 6mM.

Answer 52

c) 2mM.

Question 53

T or F: In eukaryotes, the 3’ end of the mRNA is associated with the 5’ end during initiation, whereas in prokaryotes, it is not.

Answer 53

T

Question 54

T of F: In prokaryotes, it is initiated at an AUG near a Shine-Dalgarno sequence in the mRNA, whereas in eukaryotes, it is initiated at an AUG near the 3’ end of the mRNA.

Answer 54

F

Question 56

T or F: In prokaryotes, it is initiated with Met, whereas in eukaryotes, it is initiated with fMet.

Answer 56

F