DNA replication

Question 1

How is the parental DNA read when its a template?

Answer 1

As 3’–> 5’ as the new strand is being synthesised in the 5’ –> 3’

Question 2

What are origins of replication?

Answer 2

A-T rich areas where DNA replication begins. it starts here because its easier to break 2 H bonds rather than 3

Question 3

Why are there multiple origins of replication in Eukaryotic cells?

Answer 3

Lots of DNA and it would take too long if we only started at one pt

Question 4

What direction does DNA repllication go?

Answer 4

Bidirectional from OoR

Question 5

What is the replication bubble?

Answer 5

Bubble formed where Parental and newly synthesised DNA forms

Question 6

What is the leading strand

Answer 6

Continuously synthesised in the 5’ –> 3’ direction

Question 7

What is the lagging strand

Answer 7

semidiscontinuous, creating as 5’–> 3’ fragments called Okazaki

Question 8

Which protein breaks the AT bonds and pulls apart the DNA?

Answer 8

Helicase

Question 9

What does RNA primase do?

Answer 9

Gives a starting point for DNA replication by creating a short strand of nucleotides (RNA primer) with a 3’ OH group as the starting point

Also inserts U instead of T

Question 10

What does DNA polymerase III do?

Answer 10

Starts at the RNA primer, attatches the phosphate and lays down nucleotides that are complementary to the template

Question 11

What does topoisomerase do?

Answer 11

It releases the tension ahead of the replication fork by cutting and rejoining the strands (prevents them from getting wound up)

Question 12

What is ssbp

Answer 12

Single Stranded DNA Binding Proteins

Question 13

What do ssbp’s do?

Answer 13

• Prevent complementary template strands from snapping back into position
  *Protects the exposed nucleotides from degradation i.e attack from outer enzymes

Question 14

What does DNA polymerase I do?

Answer 14

It removes the RNA primer (even to the original leading strand) and extends the end of the OH- to the phosphate group

Question 15

What does Ligase do?

Answer 15

Connects the OH- and the phosphate with a phosphodiester bond

Question 16

Which protein corrects errors during replication?

Answer 16

EXOnuclease, used by DNA pol III when it accidentally adds a wrong base, just replaces it

Question 17

Which protein corrects errors after replication?

Answer 17

ENDOnuclease, doesn’t have fine motor skills so it just takes out a whole as chunk w the incorrect base and then fills in the correct bases. Ligase joins them together later.

Question 18

Purpose of PCR

Answer 18

*Replicates a target strand of DNA using heating and cooling cycles, this gives us enough target material to work with

Question 19

Steps of PCR

Answer 19

*Denaturation
*Annealing
*Extension

Question 20

What happens in denaturation?

Answer 20

Heat is applied to break the hydrogen bonds

Question 21

What happens in Annealing?

Answer 21

Presynthesised RNA primers are added, temp is lowered and the primers find its correcponding DNA bits and forms H bonds with them. Temp is not lowered too much otherwise DNA snaps back into place