DNA synthesis

Question 0

The site at which replication occurs is called the _______

Answer 0

replication fork

Question 1

Each of the two parental strands of DNA serve as a template for the synthesis of a ______

Answer 1

complementary strand

Question 2

_______ and ________ are required to unwind the DNA helix of the parental strands

Answer 2

Helicases and Topoisomerases

Question 3

________ is the major enzyme involved in repilcation. It’s function is to……

Answer 3

DNA polymerase: copies parental/template strands in the 3’ to 5’ direction, producing new strands in the 5’ to 3’ direction

Question 4

DNA polymerase requires a …..(think primers…)

Answer 4

3’ Hydroxyl group of the primer.

***primer synthesized by primase (RNA primer)

Question 5

The precursors for replication are ______

Answer 5

deoxyribonucleotide triphosphates (sugar, base, phosphates)

Question 6

DNA synthesis proceeds in the _______ direction meaning that….

Answer 6

5’ to 3’ –> one strand continuously, other discontinuously creating small fragments because DNA must synthesize in the 5’ to 3’ direction

Question 7

Replication is semiconservative, meaning…

Answer 7

each daughter chromosome contains one parental and one new

Question 8

With the addition of a new deoxyribonucloside triphosphate (NUCLEOTIDE) via a phosphodiester bond a ________ is released. Why is this important?

Answer 8

pyrophosphate (PPi)—-The deltaG of PPi = -30KJ which drives the reaction forward. Energetically favorable.

Question 9

Prokaryotes->Initiation of DNA replication (circular ds) starts at _________

Answer 9

binding protein DnaA

**at a Single point of origin, OriC

Question 10

P-> synthesis begins at OriC and occurs at two ….. that move away from the origin ________

Answer 10

two asymmetrical Y-shaped rep forks–> bidirectionally

Question 11

P–> replication ends at ______

Answer 11

termination point on opposite side of circular chromosome

** multiple rounds occurring at same time

Question 12

P-Major initiator protein is ________

Answer 12

DnaA

Question 13

P-Helicases (______) separate DNA strands and unwind parental duplex

Answer 13

DnaB

Question 14

P-________ prevent the strands from re-associating and protects strand from cleaving proteins

Answer 14

single-stranded binding proteins

Question 15

P-_______ are enzymes that can break phosphodiester bonds and rejoin them to relive the supercoiling tension caused by unwinding

Answer 15

topoisomerases

**DNA GYRASE in bacteria

Question 16

On leading strand DNA poly moves ______ on the template creating new strand in ______ direction—-> CONTINUOUS

Answer 16

3’ to 5’ on template

new strand 5’ to 3’

Question 17

On the lagging strand _______ are created in the _______ direction

Answer 17

Okazaki Fragments; 5’ to 3’

*fragments ligated together

Why? Because daughter strands can ONLY be made in the 5’ to 3’ direction so there must be a lagging strand

Question 18

On the lagging strand there are multiple ______ and after DNA poly adds to it the ______fragments are produced that are ligated together by ______

Answer 18

RNA primers; Okazaki fragments; Ligase

Question 19

DNA poly can’t lay down without _____ from RNA primer/ DNA primase

Answer 19

3’ Hydroxyl

Question 20

Clamp proteins prevent….

Answer 20

DNA poly from falling off template strand

Question 21

Polymerases typically have a ______function that….(important for errors)

Answer 21

proofreading function detecting/correcting incorrect bases

Question 22

RNA primers are removed from Okazaki fragments by ______ and RNAase H. It then fills in gaps left from the removal and ______joins in to join the two chains together

Answer 22

Poly I ; DNA ligase

Question 23

Pol I —> (think Okazaki)
Pol II—>
Pol III —>

Answer 23

I–> fill in gaps, remove RNA primer, DNA repair
II–> DNA repair
III –> DNA REPLICATION

Question 24

DNA synth is similar in eukaryotes but with more proteins and the complication of having to replicate through _______. Different regions of chromosomes replicate at different times in cell cycle (S phase) unlike Prokaryotes that replicate continuously.

Answer 24

nucleosomes

Question 25

Unlike prokaryotes, eukaryotes have multiple….. which appear as bubbles

Answer 25

multiple points of origin of rep

Question 26

Eukaryotes have 15 different polymerases; Poly-___ is the major replicative enzyme

Answer 26

Poly Delta

Question 27

Topoisomerase I –> enzyme that transiently forms a single covalent bond with DNA to allow free rotation of DNA. Think of this as the “_____” reaction of a SINGLE strand

Answer 27

Nicking

Question 28

Topoisomerase II —> Think of this one as the ______ because it breaks BOTH strands and fixes the break

Answer 28

Magic Rope trick

**increased expression in Cancer cells–> anticancer drug target

Question 29

End of replication problem…..

How to fix it?

Answer 29

after replication the lagging strand cannot be finished resulting in a 3’ overhang–> TELOMERASE uses RNA primer to lengthen 3’ strand

Question 30

Telomerase adds a short piece of DNA, a ______, that is lost when a cell divides and DNA is replicated

Answer 30

telomere

Question 31

Telomerase is an example of _______ because….

Answer 31

Reverse Transcriptase because it crease a ssDNA from an RNA template

Question 32

Telomerase with bound RNA template adds DNA nucleotides to _____strand to allow DNA polymerase to complete the lagging strand

Answer 32

Parental Strand (leading strand)

Question 33

What type of cells produce lots of telomerase?

Little amounts?

Answer 33

embryonic cells to allow them to indefinitely divide

Somatic express little, decreasing with time

Question 34

_____cells upregulate telomerase.Therefore making it a drug target.

Answer 34

Cancer Cells