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MCAT-BIOLOGY > Molecular Biology-DNA Replication > Flashcards

Molecular Biology-DNA Replication Flashcards

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1
Q

replication

A

cell division involved in duplication of DNA

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2
Q

when does replication occur?

A

during S phase (synthesis) in the interphase of the cell

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3
Q

parental DNA

A

the old DNA

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4
Q

daughter DNA

A

new DNA

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5
Q

conservative replication

A

the parental ds-DNA would remain as it is while an entirely new ds-genome was created

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6
Q

dispersive theory

A

both copies of the genomes were composed of scattered pieces of new and old DNA

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7
Q

replication is semiconservative:

A

after replication, one strand of the new double helix is parental (old) and one strand is the newly synthesized daughter strand

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8
Q

helicase

A

the enzyme that unwinds the double helix and separates the strands

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9
Q

origin of replication (ORI)

A

the sequence where helicase begins to unwind, recognized by specific proteins

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10
Q

which protein recognizes ORI in prokaryotes?

A

DnaA

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11
Q

which protein recognizes ORI in eukaryotes?

A

there are three proteins: two of which are synthesized in M and G1 phase but rapidly destroyed once the S phase begins; this links DNA replication to the cell cycle, ensuring DNA replication doesn’t initiate during other phases of the cycle

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12
Q

topoisomerases

A

cut one or both of the ds DNA strands and unwrap the helix to release excess tension created by helicase

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13
Q

single-strand binding proteins (SSBPs)

A

protect DNA that has been unpackaged in preparation for replication and help keep the strands separated

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14
Q

open complex

A

separated strands of DNA complex

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15
Q

primase

A

an RNA polymerase that synthesizes RNA primer

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16
Q

DNA extension requires:

A

an RNA primer; DNA polymerase can only add onto an existing chain

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17
Q

DNA polymerase (DNA pol)

A

catalyzes the elongation of the daughter strand using the parental template and elongates the primer by adding dNTP’s to its 3’ end

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18
Q

in the polymerization reaction, what acts as the nucleophile?

A

3’ hydroxyl group to displace 5’ pyrophosphate from the dNTP to be added

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19
Q

DNA pol is part of a large complex of proteins called:

A

replisome-components/accessory proteins help DNA polymerase and allow it to polymerize DNA quickly

20
Q

why do eukaryotes have a larger replisome containing more proteins?

A

because of complexity of eukaryotic system; requires unwinding of DNA from histone proteins

21
Q

what is the thermodynamic driving force of the polymerization reaction?

A

the removal and hydrolysis of pyrophosphate (P2O7) from each dNTP added to the chain

22
Q

which direction does polymerization occur?

A

5’ to 3’ (WITHOUT EXCEPTION)

23
Q

what does DNA pol require?

A

a template and a primer

24
Q

in which direction is the template strand read?

A

3’ to 5’

25
Q

replication fork

A

the area where the parental double helix unwinds

26
Q

leading strands

A

able to elongate continuously into the widening replication fork

27
Q

lagging strand

A

must wait until the replication fork widens before beginning to polymerize, forms fragments

28
Q

Okazaki fragments

A

the chunks of DNA that comprise the lagging strand

29
Q

in which direction does the replication fork grow?

A

in both directions, away from the origin. Each replication fork contains a leading strand a lagging strand

30
Q

replication of the leading strand is:

A

continuous

31
Q

replication of the lagging strand is:

A

discontinuous, results in Okazaki fragments

32
Q

eventually, what happens to RNA primers?

A

they are replaced by DNA and the fragments are joined by DNA ligase

33
Q

DNA pol III

A

super-fast & super-accurate elongation of the leading strand (high processivity), exonuclease activity, no known function in repair

34
Q

proofreading function

A

the ability to correct mistakes by 3’ to 5’ exonuclease activity

35
Q

DNA pol I

A

starts adding nucleotides at the RNa primer, poor processivity (slow), exonuclease/proofreading, removes RNA primer via exonuclease activity while leaving behind new DNA, important for excision repair

36
Q

DNA pol II

A

5’ to 3’ polymerase activity, exonuclease/proofreading, participates in DNA repair pathways, backup for pol III

37
Q

DNA pol IV and DNA pol V

A

error prone in polymerase activity, function to stall other polymerase enzymes at replication forks when DNA repair pathways have been activated (important part of prokaryotic checkpoint activity)

38
Q

how many chromosomes and origins do prokaryote chromosomes have?

A

only one chromosome with only one origin

39
Q

theta mechanism/theta replication

A

describes the replication process of prokaryotes

40
Q

how many origins do eukaryotic chromosomes have?

A

several; eventually the replication forks will meet and the daughter strands will be ligated together

41
Q

what happens if telomeres become too short?

A

they reach a critical length when the chromosome can no longer replicate. cell can either activate a senescent state or apoptosis

42
Q

Hayflick limit

A

the number of times a normal human cell type can divide until telomere length stops cell division

43
Q

telomerase

A

enzyme that adds repetitive nucleotide sequences to the ends of chromosomes and lengthens telomeres

44
Q

telomerase is a ribonucleoprotein complex that contains:

A

an RNA primer and a reverse transcriptase enzyme; polymerases and then translocates to allow for extension of telomere repeats

45
Q

reverse transcriptase

A

read RNA and generate DNA, allows for chromosome exntesion

MCAT-BIOLOGY (17 decks)

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