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Molecular Biology > Lecture 2: DNA Replication > Flashcards

Lecture 2: DNA Replication Flashcards

1
Q

Where does DNA replication occur in bacteria?

a) Nucleus
b) Cytoplasm
c) Mitochondria
d) Chloroplasts

A

b) Cytoplasm

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2
Q

What is the typical structure of bacterial DNA?

a) Linear and multiple chromosomes
b) Circular and a single chromosome
c) Circular and multiple chromosomes
d) Linear and a single chromosome

A

b) Circular and a single chromosome

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3
Q

How many origins of replication do bacterial chromosomes typically have?

a) None
b) One
c) Two
d) Multiple

A

b) ONE

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4
Q

Which protein initiates DNA replication in bacteria?

a) ORC (Origin Recognition Complex)
b) DnaA protein
c) Cdc6
d) MCM helicase

A

B) DnA protein
- it binds to specific sequences at OriC (Origin of replication)

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5
Q

Which DNA polymerase is primarily responsible for the bulk of DNA synthesis in bacteria?

a) DNA polymerase I
b) DNA polymerase II
c) DNA polymerase III
d) DNA polymerase α

A

C)

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6
Q

What is the typical size of Okazaki fragments in eukaryotic DNA replication?

a) 100-200 nucleotides
b) 1000-2000 nucleotides
c) 50-100 nucleotides
d) 500-1000 nucleotides

A

a) 100 to 200

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7
Q

Which of the following is a key difference in the initiation of DNA replication between eukaryotes and bacteria?

a) Eukaryotes have circular DNA.
b) Bacteria use multiple DNA polymerases.
c) Eukaryotes form a pre-replication complex at the origin.
d) Bacterial replication occurs in the nucleus.

A

c)

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8
Q

What enzyme is responsible for synthesizing RNA primers in eukaryotic DNA replication?

a) DNA polymerase ε
b) DNA polymerase α
c) DNA polymerase δ
d) Primase

A

b)

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9
Q

During DNA replication, which of the following statements correctly describes the incorporation of a deoxyribonucleoside triphosphate (dNTP) into the growing DNA strand?

A) The pyrophosphate released from the dNTP is incorporated into the DNA strand, while the α-phosphate is discarded.

B) The 3’ OH group of the growing DNA strand attacks the β-phosphate of the dNTP, resulting in the incorporation of the β-phosphate into the DNA.

C) The α-phosphate of the dNTP is incorporated into the DNA strand, while the pyrophosphate (PPi) is released and hydrolyzed, providing energy for the reaction.

D) The dNTP enters the reaction as a monophosphate, and the three phosphates are all incorporated into the DNA strand.

A

c)

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10
Q

True or False: The replication Fork in prokaryotes is circular

A

True!

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11
Q

What are the short segments of DNA that are synthesized discontinuously on the lagging strand during DNA replication called?

A) Leading strands

B) Primer fragments

C) Okazaki fragments

D) RNA fragments

A

c) Okazaki fragments

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12
Q

What is the primary role of DNA polymerase during DNA replication?

A) To synthesize RNA primers
B) To add nucleotides to a growing DNA strand
C) To unwind the DNA double helix
D) To remove RNA primers

A

b)

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13
Q

Why does DNA polymerase need a 3’ hydroxyl (OH) group?

A) To initiate DNA synthesis
B) To terminate DNA synthesis
C) To provide a site for nucleotide addition
D) To stabilize the DNA structure

A

C) To provide a site for nucleotide addition

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14
Q

What is the function of DNA primase?

A) To synthesize DNA strands
B) To synthesize RNA primers
C) To repair DNA damage
D) To remove RNA primers

A

b)

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15
Q

On which strand does DNA synthesis occur continuously?

A) Lagging strand
B) Leading strand
C) Both strands
D) Neither strand

A

b) leading strand

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16
Q

What is created at the beginning of each Okazaki fragment?

A) A new DNA strand
B) A RNA primer
C) A protein complex
D) A single nucleotide

A

B) A RNA primer

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17
Q

What provides the energy to initiate the DNA synthesis reaction during replication?

A) Release of ATP
B) Pyrophosphate group release
C) Helicase activity
D) RNA primer synthesis

A

b)Pyrophosphate group release (gets released when new nucleotide added to daughter strand)

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18
Q

What kind of replication does DNA undergo?

A) Conservative replication
B) Semiconservative replication
C) Dispersive replication
D) Unidirectional replication

A

B) Semiconservative

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19
Q

What is the role of DNA ligase during DNA replication?

A) Unwinds the DNA double helix
B) Joins Okazaki fragments by forming phosphodiester bonds
C) Synthesizes RNA primers
D) Removes RNA primers

A

B)

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20
Q

Which protein stabilizes the single-stranded DNA during replication?

A) Helicase
B) Single-stranded binding protein (SSB)
C) Topoisomerase
D) Sliding clamp

A

B) SSBs

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21
Q

In prokaryotic cells, which initiator protein binds to the origin of replication?

A) DnaB
B) DnaA
C) DnaC
D) Primase

A

B) DnA

22
Q

Which enzyme relieves the stress caused by DNA unwinding during replication?

A) Helicase
B) Topoisomerase
C) DNA polymerase
D) Primase

A

B) Topoisomerase

23
Q

What is the primary function of the sliding clamp in DNA replication?

A) To unwind the DNA double helix
B) To remove RNA primers
C) To keep DNA polymerase attached to the DNA strand
D) To synthesize the leading strand

A

c)

24
Q

What is the source of energy that the clamp loader uses to load the sliding clamp onto the DNA?

A) GTP
B) ATP
C) Pyrophosphate
D) ADP

A

ATP

25
Q

What does the structure of the clamp loader resemble?

A) A helicase
B) A screw nut
C) A straight rod
D) A fork

A

B) Screw Nut

26
Q

How does the sliding clamp help increase the processivity of DNA polymerase?

A) By facilitating the incorporation of correct nucleotides
B) By preventing the DNA strand from tangling
C) By preventing DNA polymerase from dissociating from the DNA strand during replication
D) By allowing DNA ligase to bind efficiently to the DNA strand

A

C)

27
Q

Why is it important for the sliding clamp to “recognize” the newly synthesized region of DNA?

A) To terminate the replication process at the correct location
B) To ensure that the correct RNA primer is removed
C) To allow the sliding clamp to hold DNA polymerase in place during elongation
D) To enable topoisomerase to relieve torsional stress in the DNA strand

A

c)

28
Q

How does the sliding clamp assist in the replication of both the leading and lagging strands?

A) It only assists in the leading strand, while a different mechanism is used for the lagging strand
B) It remains bound to the DNA indefinitely during leading strand synthesis, but dissociates and reassembles during lagging strand synthesis to start a new Okazaki fragment
C) It binds to the RNA primer on both strands to initiate replication
D) It interacts with topoisomerase to prevent DNA tangling on both strands

A

b)

29
Q

DNA ligase is primarily responsible for joining which of the following during DNA replication?

A) Leading strand segments
B) Okazaki fragments on the lagging strand
C) RNA primers with DNA nucleotides
D) DNA helicase with DNA polymerase

A

B)

30
Q

What happens to ATP during the DNA ligase reaction?

A) It is converted into AMP and pyrophosphate
B) It is stored for later use
C) It is used to unwind DNA
D) It is released without being hydrolyzed

A

A)

31
Q

Which of the following bonds does DNA ligase specifically catalyze the formation of?

A) Hydrogen bonds between base pairs
B) Phosphodiester bonds in the sugar-phosphate backbone
C) Covalent bonds between RNA nucleotides
D) Peptide bonds between amino acids

A

B)

32
Q

After DNA ligase joins DNA fragments, what molecule is released?

A) Pyrophosphate (PPi)
B) Guanosine triphosphate (GTP)
C) Adenosine diphosphate (ADP)
D) Uridine monophosphate (UMP)

A

A) PPi

33
Q

What is the primary role of Topoisomerase I during DNA replication?

A) To unwind the DNA double helix
B) To prevent supercoiling by allowing free rotation of the DNA
C) To cut both strands of DNA
D) To synthesize RNA primers

A

B)

34
Q

What distinguishes Topoisomerase II from Topoisomerase I?

A) Topoisomerase II allows free rotation without cutting DNA
B) Topoisomerase II cuts both DNA strands and requires energy
C) Topoisomerase II is involved only in RNA synthesis
D) Topoisomerase II does not require energy to function

A

B)

35
Q

Topisomerase II is also known as ______.

Fill in the blank

A

DNA Gyrase

36
Q

Explain the function of Tpoisomerase II.

SA

A

Topoisomerase II (or DNA gyrase) is an enzyme that plays a crucial role in relieving the torsional strain that builds up ahead of the replication fork during DNA replication. As the DNA double helix unwinds, supercoils form, which can hinder the replication process. Topoisomerase II functions by cutting both strands of the DNA, allowing one strand to pass through the break. This untangles the DNA and releases the supercoiling tension. Afterward, the enzyme reseals the DNA strands, ensuring that the replication process can continue smoothly. This process requires energy in the form of ATP.

37
Q

The initiator protein that binds to specific AT-rich sequences at the origin of replication is called __________.

Fill in the blank

A

DnA

38
Q

In bacteria replication, which proteins inhibit the helicases until they are properly loaded at the origin of replication?
A) DnaA proteins
B) DnaC proteins
C) DnaG proteins
D) DNA polymerases

A

B) DnaC proteins

39
Q

The specific sequence at the origin of replication where DnaA binds is referred to as __________.

Fill in the blank

A

oriC

40
Q

What is the role of DnG and which cell does it reside in?

A

DnG sythesizes inital primers and resides in bacterial cells
it is a bacterial protein

41
Q

The most important structural difference between eukaryotic and bacterial DNA is that eukaryotic DNA is __________, while bacterial DNA is __________.

A

Linear; Circular

42
Q

In eukaryotic organisms, why are there multiple origins of replication?
A) To ensure DNA is replicated only once
B) To speed up the replication process
C) To prevent errors during replication
D) To allow for more mutations

A

B) To speed up the replication process

43
Q

Which strand is referred to as the leading strand during DNA replication in Eukaryotic cells?
A) The strand with a free 5’ end
B) The strand that is synthesized discontinuously
C) The strand with a free 3’ end
D) The strand that requires multiple primers

A

C) The strand with a free 3’ end

44
Q

In eukaryotic DNA replication, the formation of a replication bubble occurs at many origins of replication to ensure that the entire genome is replicated in a timely manner; each replication bubble has two replication forks that move in __________ directions.

A

opposite

45
Q

What is the primary role of DNA polymerase alpha primase in eukaryotic DNA replication?
A) To complete Okazaki fragments
B) To extend the leading strand
C) To initiate DNA replication at the origin
D) To proofread the newly synthesized DNA

A

c)

46
Q

Which of the following DNA polymerases in eukaryotes is responsible for extending the leading strand?
A) Pol (Alpha)
B) Pol (Delta)
C) Pol (Epsilon)
D) Pol (Beta)

A

C) Pol - Epsilon

47
Q

In eukaryotic cells, the polymerase called __________ is involved in completing Okazaki fragments on the lagging strand.

A

Pol (Delta)

48
Q

Unlike prokaryotes, eukaryotic DNA replication must also occur through __________ due to the complex packaging of DNA

A

Nucleosomes

49
Q

you determine that the double-stranded DNA of an organism you have discovered is composed of 24% G bases. What percent is T?
a) 24%
b) 26%
c) 56%
d) 16%
e) insuffcient info given

A

b)

50
Q

compared to the human genome the genome of yeast typically has…
a) more introns
b) higher fraction of coding DNA
c) more repetitive DNA
d) longer genes
e) longer chromosomes

A

b)

51
Q

During DNA replication in the cell, DNA primase makes short primers that are then extended by the replicative DNA polymerase. These primers…
a) are made up of DNA
b) provide a 3’ phosphate group for the DNA polymerase to extend
c) are made more frequently in the leading strand than the lagging strand
d)are joined to the neighboring DNA by DNA ligase
e) generally have a higher number of mutations compared to neighboring DNA

A

e)

52
Q
A

Molecular Biology (9 decks)

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