Replication of DNA and Chromosomes

Question 1

What are the complementary base pairs of DNA

Answer 1

A and T
C and G

Question 2

How many H-bonds connect C and G

Answer 2

3

Question 3

How many H-bonds connect A and T

Answer 3

2

Question 4

How many base pairs per turn in a double helix

Answer 4

10

Question 5

Is a double helix left handed or right handed

Answer 5

right handed

Question 6

Is DNA conservative, semi-conservative, or non conservative

Answer 6

semi conservative

Question 7

What does it mean that DNA is semi-conservative?

Answer 7

when DNA replicates, one strand is conserved while a new complementary strand is made, forming a new double strand containing one conserved and one new strand

Question 8

What is theta replication

Answer 8

replication that occurs in circular DNA

Question 9

How does theta replication occur

Answer 9

DNA unwinds at the replication origin which produces single-stranded templates for the synthesis of new DNA, and the fork proceeds around the circle from both directions simultaneously
- this process is bidirectional**

Question 10

What is the final product of theta replication

Answer 10

two circular DNA molecules are produced (from one original circular DNA)

Question 11

What is rolling circle replication

Answer 11

specialized form of replication that only occurs in the F factor of some viruses

Question 12

What is different about the origin of replication between theta replication and rolling circle replication

Answer 12

theta - origin of replication is a fork of the double stranded DNA, resulting in bidirectional replication on strands
rolling circle - replication is initiated at a break in one DNA strand and synthesis begins at the 3’ end of the break

Question 13

How does rolling circle replication work

Answer 13

a break occurs in one strand of the circular DNA, and synthesis of new DNA occurs at the 3’ end of the break while the 5’ end is continually displaced as the strand builds
- once the new strand has synthesized around the whole circle, cleavage occurs and the newly synthesized strand replaces the old strand on the circle

Question 14

What makes rolling circle replication repetitive/continuous

Answer 14

the 5’ end of the original strand that is eventually cleaved folds back into its circular form and can be used as a template for another set of replication

Question 15

Is rolling circle replication bidirectional or unidirectional

Answer 15

unidirectional

Question 16

What is linear chromosome replication

Answer 16

occurs in the linear chromosomes of eukaryotic cells: at the various origins on the linear strand, replication bubbles are formed and synthesis occurs on both strands in both directions until eventually, the various bubbles run into each other and fuse producing two identical molecules of linear DNA

Question 17

Is linear chromosome replication unidirectional or bidirectional

Answer 17

bidirectional

Question 18

What is special about linear chromosome replication (thinks in term of origin)

Answer 18

unlike theta and rolling circle (only have one point of origin), linear chromosome replication has various origin sites that simultaneously synthesize DNA

Question 19

What are some requirements of DNA replication

Answer 19

• DNA polymerase
• dNTPs
• single strand to be copied
• an RNA primer

Question 20

What direction does DNA synthesis occur

Answer 20

5’ - 3’

Question 21

What are the features of newly synthesized DNA when compared to its original strand

Answer 21

complementary and antiparallel

Question 22

How is a double strand of DNA held together

Answer 22

H-bonds between base pairs

Question 23

In a replication fork, does synthesis on the two strands occur in the same direction or opposite

Answer 23

opposite

Question 24

Why does synthesis occur in opposite directions on the two strands in a replication fork

Answer 24

because two template strands are antiparallel and synthesis is always 5’-3’ so one will synthesize in one direction, one will synthesize in the other

Question 25

What is the issue with synthesis on the lagging strand

Answer 25

as per the name, it is lagging, so DNA synthesizes in fragments instead of one continuous strand

Question 26

What are the fragments called created by the lagging strand

Answer 26

Okazaki fragments

Question 27

Which type of replication does not have lagging strands

Answer 27

rolling circle (only one strand being synthesized at a time)

Question 28

What are DnaA proteins in prokaryotic replication

Answer 28

initiator proteins that bind to oriC

Question 29

What does the binding of DnaA and oriC result in in prokaryotic replication

Answer 29

short stretch of DNA to unwind

Question 30

What is oriC

Answer 30

the origin of replication in prokaryotes

Question 31

What are some proteins involved in prokaryotic replication

Answer 31

- DNA helicase - DNA gyrase - single stranded binding proteins - primase - DNA polymerase (1 and 3) - DNA ligase

Question 32

What is the function of helicase in prokaryotic DNA replication

Answer 32

unwinds DNA in a 5'-3' direction only on the lagging strand ahead of replication (binds to single strand)

Question 33

What is the function of DNA gyrase in prokaryotic replication

Answer 33

a topoisomerase that makes double stranded breaks in the DNA to relieve strain that builds up from helicase activity - binds upstream of unwinding fork to prevent torsion

Question 34

What is the function of single stranded binding proteins in prokaryotic replication

Answer 34

coats unwound single stranded DNA to keep it single stranded and prevent hairpins

Question 35

What is the function of primer in prokaryotic replication

Answer 35

synthesizes a short RNA primer that provides 3'OH end for DNA poly to begin synthesis - primase binds directly to helicase

Question 36

What is the function of DNA polymerase 3 in prokaryotic replication

Answer 36

the main polymerase* - has 5'-3' poly activity and 3'-5' exonuclease activity - adds dNTPs to the 3' end but can also backup to remove a nucleotide that has been misincorperated

Question 37

What is the function of DNA polymerase 1 in prokaryotic replication

Answer 37

similar to poly 3, except poly one ALSO has 5'-3' exonuclease activity so it can remove the RNA primer and replace it with DNA

Question 38

What is the basic function of DNA poly 1

Answer 38

remove primers

Question 39

What is the basic function of DNA poly 2

Answer 39

DNA repair (restarts synthesis after repair has occurred)

Question 40

What is the basic function of DNA poly 3

Answer 40

Elongating DNA

Question 41

What is the basic function of DNA poly 4

Answer 41

DNA repair

Question 42

What is the basic function of DNA poly 5

Answer 42

DNA repair (translesion DNA synthesis)

Question 43

What protein actually synthesized the DNA

Answer 43

DNA polymerase

Question 44

What is the function of DNA ligase

Answer 44

joins Okazaki fragments together to form a continuous strand of DNA

Question 45

Where does synthesis begin in eukaryotic replication

Answer 45

autonomously replicating sequences (AT rich)

Question 46

How is helicase different in eukaryotic replication

Answer 46

binds to double-strand (instead of single)

Question 47

What is different about the Okazaki fragments and RNA primers in eukaryotic replication

Answer 47

longer RNA primers, shorter Okazaki fragments

Question 48

What phase does replication occur in eukaryotes

Answer 48

S phase

Question 49

What is different about DNA poly in eukaryotes

Answer 49

many polymerases (at least 15)

Question 50

What is the function of polymerase alpha in eukaryotes

Answer 50

primase acitvity

Question 51

What is the function of polymerase epsilon in eukaryotes

Answer 51

leading strand replication

Question 52

What is the function of polymerase delta in eukaryotes

Answer 52

lagging strand replication

Question 53

What occurs with nucleosomes in eukaryotic replication

Answer 53

need to be removed from parental DNA and reassembled on newly synthesized DNA

Question 54

What occurs with telomeres in eukaryotic replication

Answer 54

shorten with each round

Question 55

Where does origin licensing occur and what does that entail

Answer 55

means preparation for replication in eukaryotes - occurs in the G1 phase - replication licensing factors attach to each origin site

Question 56

What is the purpose of origin licensing

Answer 56

prep DNA for replication and prevent re-initiation of replication

Question 57

In what phase does replication begin in eukaryotes

Answer 57

S phase

Question 58

When DNA is replicated what needs to occur with histones and what protein assists in that function

Answer 58

histone proteins must also be doubled and the modifications made to DNA must also be replicated - chaperone proteins play a key role in this function

Question 59

Why are RNA primers essential in DNA replication of circular DNA

Answer 59

circular DNA doesn't have 3' or 5' ends, so the 3' OH must be added to initiate replication in the circular DNA

Question 60

What is telomerase

Answer 60

an enzyme specific to eukaryotes that extends chromosome ends in replication cells

Question 61

How does telomerase function

Answer 61

extends the 3' end of the chromosome without the use of a complementary template, telomerase is then removed, and synthesis takes place on the complementary strand to match the newly added nucleotides (via telomerase)

Question 62

In what cells is telomerase highly present

Answer 62

highly dividing somatic cells and germ cells

Question 63

What are shorter telomeres associated with in terms of overall health

Answer 63

diseases involving premature aging