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Biochemistry (III) > DNA Replication > Flashcards

DNA Replication Flashcards

1
Q

DNA replication is ____ & ______.

A

Bidirectional and semiconservative

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2
Q

Semiconservative: each copy of the DNA molecule, after replication, contains one strand from the __________ and one from the ________

A

Original template, newly synthesized

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3
Q

Prokaryotes have ______ origin of replication and _____ DNA

A

1, circular

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4
Q

Origins of replication sequences are almost exclusively ____ and _____ bases.

A

A-T bases

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5
Q

These proteins bind to single strands to prevent reannealing and protect DNA from nuclease degradation.

A

SSBs: Single-Stranded binding proteins

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6
Q

This enzyme unwinds the DNA helix.

A

DNA Helicase

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7
Q

DNA is a helix, so when helicases separate the strands of DNA, _________ ahead of the replication fork will occur.

A

Supercoiling

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8
Q

________ alleviate supercoiling ahead of the replication fork.

A

Topoisomerases

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9
Q

____________ creates a nick in one strand which allows the DNA to swivel around the intact strand, then seals the nicked strand.

A

Type I topoisomerase

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10
Q

__________ cut both strands to relieve the supercoiling then re-ligates the two strands

A

Type II topoisomerase

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11
Q

A special Type II topoisomerase (found in bacteria), __________ - introduces (-) supercoils - inhibited by ________

**Also important for the separation of circular chromosomes after replication.

A

DNA Gyrase, quinolones

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12
Q

All polymerases that synthesize nucleic acids only catalyze synthesis in the ____ to _____ direction.

A

5’ to 3’

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13
Q

Since DNA is antiparallel, the template must be read in the ____ to _____ direction.

A

3’ to 5’

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14
Q

Nucleic Acid Synthesis direction: _______

Template Reading Direction: _______

A

5’ to 3’

3’ to 5’

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15
Q

During DNA replication, this strand is synthesized continuously.

A

Leading Strand

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16
Q

During DNA replication, this strand is synthesized discontinuously away from the replication fork.

A

Lagging Strand

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17
Q

In DNA replication, the discontinuously synthesized fragments are called _____ fragments and are later joined to become a continuous segment of DNA

A

Okazaki

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18
Q

DNA polymerases require a free _________group to begin synthesis.

During DNA replication, this problem is solved by the action of ________.

A

3’ hydroxyl, Primase

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19
Q

Primase is an ____________ and does not require a free 3’ OH group to begin synthesis. It copies the first ~10 nucleotides to prime synthesis.

DNA polymerases then begin synthesis from the free 3’OH group from the RNA primer.

A

RNA polymerase

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20
Q

Each new DNA fragment on the lagging strand begins with the action of ________ laying down an _______

A

Primase, RNA primer

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21
Q

________ recognizes the RNA primer and begins to synthesize the DNA

A

DNA polymerase III

22
Q

___________ catalyze a reaction between the 3’OH group of the strand being synthesized and the ______________ of an incoming nucleotide specified by the template being copied.

A

DNA polymerases, 5’ triphosphate

23
Q

Net reaction of DNA Polymerase = addition of a ______ to a growing DNA strand and the release of __________.

_________ is further cleaved to _____________ to make the reaction irreversible and drive the reaction in the forward direction.

A 
Nucleotide, pyrophosphate, Pyrophosphate, 
inorganic phosphate (Pi)
24
Q

_______ - a common theme in many condensation reactions in biochemistry

A

A coupled irreversible reaction -

25
Q

_______ high energy bonds are cleaved for each added nucleotide in a growing DNA chain.

A

2

26
Q

________ is the enzyme in prokaryotes that elongates both the leading and lagging strands

A

DNA polymerase III

pol III

27
Q

DNA polymerase III (pol III) is the enzyme in _________ that elongates both the leading and lagging strands.

A

Prokaryotes

28
Q

DNA replication needs to be as accurate as possible - a single nucleotide mutation can have devastating consequences. Pol III, as well as many other DNA polymerases, have ______ _____

A

Proofreading Activity

29
Q

If DNA polymerase mispairs a nucleotide with the template, it uses its ________ to excise the mismatched nucleotide.

A

3’ to 5’ exonuclease activity

30
Q

________ checks each added nucleotide to make sure it is correctly base-paired with the template strand.

A

Pol III

31
Q

When pol III detects a mistake, it __________ one nucleotide and she’s the misincorporated nucleotide.

This is called ________

A

Shifts backward

3’ to 5’ exonuclease activity

32
Q

This enzyme has 5’ to 3’ polymerase activity, and exonuclease activity in BOTH the 3’ to 5’ and 5’ to 3’ directions

A

DNA polymerase I (pol I)

33
Q

RNA primer is elongated by ______ until another stretch of RNA is encountered.

RNA primer is excised by ______, one ribonucleotide at a time.

Gap is filled by _____.

Remaining nick is sealed by ______.

A

DNA polymerase III

DNA polymerase I

DNA polymerase I

DNA-ligase

34
Q

_______ lays down an RNA primer to begin each new strand.

A

Primase

35
Q

______ extends the leading and lagging strands.

A

Pol III

36
Q

________ removes RNA primers and replaces them with DNA.

A

Pol I

37
Q

In Eukaryotic Cell Cycle, this phase is the most variable in terms of time, growth, and metabolism

A

G1 Phase (G stands for gap)

38
Q

This phase occurs when DNA is replicated.

A

S Phase (S stands for synthesis)

39
Q

This phase has a second “gap” phase where the cell prepares to divide.

A

G2 Phase

40
Q

This phase is the phase of Cell Division.

A

M phase (M for Mitosis)

41
Q

Eukaryotic DNA Polymerases:

Pol (alpha) - contains ______ + ______ (begins strand synthesis)

Pol (delta) - _______ + _______ (extends strands)

A

Primase + DNA polymerase

DNA polymerase + proofreading

(Know that alpha and delta cooperate)

42
Q

Eukaryotic chromosomes are _______. At the end of the DNA molecule, the _______ strand will have a gap once the ________ is removed.

Eukaryotes solve this problem by the action of enzymes called _______.

A

Linear
Lagging
RNA Primer
telomerases

43
Q

The ends of eukaryotic chromosomes contain repeated sequences called ______.

A

Telomeres.

44
Q

___________ extends the ends of linear chromosomes.

A

Telomerase

45
Q

Telomerase also contains a _________ - it copies its own template (RNA) into DNA extending the 3’ overhang on the chromosome. This process is repeated many times.

A

Reverse transcriptase

46
Q

Cells that do not express _______ have their chromosomes shortened after every cellular division (cellular equivalent of aging)

A

Telomerase

47
Q

A defect in mismatch repair is responsible for ____________, one of the most common inherited cancers.

A

HNPCC

Hereditary nonpolyposis colorectal cancer

48
Q

UV light usually causes pyrimidine dimers - usually _____ dimers.

A

Thymine

49
Q

In humans, a rare genetic disorder called ____ _____ most often results from a deficiency in excision endonuclease.

A

Xeroderma pigmentosum

50
Q

In humans, a rare genetic disorder called xeroderma pigmentosum most often results from a deficiency in ______ ______.

A

Excision endonuclease.

Biochemistry (III) (8 decks)

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