Molecular Biology-DNA Replication

Question 1

replication

Answer 1

cell division involved in duplication of DNA

Question 2

when does replication occur?

Answer 2

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

Question 3

parental DNA

Answer 3

the old DNA

Question 4

daughter DNA

Answer 4

new DNA

Question 5

conservative replication

Answer 5

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

Question 6

dispersive theory

Answer 6

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

Question 7

replication is semiconservative:

Answer 7

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

Question 8

helicase

Answer 8

the enzyme that unwinds the double helix and separates the strands

Question 9

origin of replication (ORI)

Answer 9

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

Question 10

which protein recognizes ORI in prokaryotes?

Answer 10

DnaA

Question 11

which protein recognizes ORI in eukaryotes?

Answer 11

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

Question 12

topoisomerases

Answer 12

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

Question 13

single-strand binding proteins (SSBPs)

Answer 13

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

Question 14

open complex

Answer 14

separated strands of DNA complex

Question 15

primase

Answer 15

an RNA polymerase that synthesizes RNA primer

Question 16

DNA extension requires:

Answer 16

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

Question 17

DNA polymerase (DNA pol)

Answer 17

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

Question 18

in the polymerization reaction, what acts as the nucleophile?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

why do eukaryotes have a larger replisome containing more proteins?

Answer 20

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

Question 21

what is the thermodynamic driving force of the polymerization reaction?

Answer 21

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

Question 22

which direction does polymerization occur?

Answer 22

5’ to 3’ (WITHOUT EXCEPTION)

Question 23

what does DNA pol require?

Answer 23

a template and a primer

Question 24

in which direction is the template strand read?

Answer 24

3’ to 5’

Question 25

replication fork

Answer 25

the area where the parental double helix unwinds

Question 26

leading strands

Answer 26

able to elongate continuously into the widening replication fork

Question 27

lagging strand

Answer 27

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

Question 28

Okazaki fragments

Answer 28

the chunks of DNA that comprise the lagging strand

Question 29

in which direction does the replication fork grow?

Answer 29

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

Question 30

replication of the leading strand is:

Answer 30

continuous

Question 31

replication of the lagging strand is:

Answer 31

discontinuous, results in Okazaki fragments

Question 32

eventually, what happens to RNA primers?

Answer 32

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

Question 33

DNA pol III

Answer 33

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

Question 34

proofreading function

Answer 34

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

Question 35

DNA pol I

Answer 35

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

Question 36

DNA pol II

Answer 36

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

Question 37

DNA pol IV and DNA pol V

Answer 37

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)

Question 38

how many chromosomes and origins do prokaryote chromosomes have?

Answer 38

only one chromosome with only one origin

Question 39

theta mechanism/theta replication

Answer 39

describes the replication process of prokaryotes

Question 40

how many origins do eukaryotic chromosomes have?

Answer 40

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

Question 41

what happens if telomeres become too short?

Answer 41

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

Question 42

Hayflick limit

Answer 42

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

Question 43

telomerase

Answer 43

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

Question 44

telomerase is a ribonucleoprotein complex that contains:

Answer 44

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

Question 45

reverse transcriptase

Answer 45

read RNA and generate DNA, allows for chromosome exntesion