Lecture 11

Question 1

What are the characteristics of a large DNA molecule replicated

Answer 1

Multiple large linear chromosomes (23 pairs in humans)
Multiple origins (starting points) of replication
bidirectional

Question 2

Where do replication bubbles begin

Answer 2

a=t double hydrogen bond region as it is easier to pull the strand apart

Question 3

What is needed in a DNA copy

Answer 3

addition of new nucleotides
a starting point for nucleotide
the unwinding of the helical double-stranded DNA.

Question 4

What happens to the leading strand in DNA replication

Answer 4

Continuously synthesised in the 5-3 direction

Question 5

What happens to the lagging strand in DNA replication

Answer 5

Discontinuously synthesised 5-3 as Okazaki fragments

Question 6

What is Primase

Answer 6

the enzyme that makes RNA primer—–starting point for DNA Polymerisation

Question 7

How does DNA polymerase III function

Answer 7

Needs an OH group onto which the phosphate group of the incoming nucleotide can be attached
only makes DNA in 5’ to 3’ direction

Question 8

How does DNA polymerase III synthesise DNA

Answer 8

it synthesises a new DNA strand by adding complementary nucleotides to the parental template strand
Cannot bind to single-stranded DNA and start copying it

Question 9

How does DNA replication initiate

Answer 9

Helicase pulls the DNA strands apart
single strand binding proteins (SSBP)- protect from enzymes and keep strand apart
Topoisomerase- cuts DNA to release tension, then rejoins it

Question 10

What does primase make

Answer 10

Makes short RNA 5-3 with OH group to react with other strands

Question 11

What does DNA polymerase III do to SSBP

Answer 11

after DNA polymerase III adds nucleotide it removes SSBP then synthesis of the leading strand continues

Question 12

How is the lagging strand synthesized

Answer 12

RNA primers from primase go 5-3, DNA polymerase III uses RNA primers to add nucelotides 5-3

Question 13

What is the role of Polymerase I

Answer 13

it recognizes the DNA, RNA hybrid strand and replaces it with nucleotides from Okazaki fragments that are not linked

Question 14

What is the role of Ligase

Answer 14

it uses 3’ OH and 5’P to create a phosphodiester bond

Question 15

how are Errors in the DNA removed

Answer 15

during-exonuclease removes errors from the 3’ or 5’ ends

after-endonuclease, chops nucleotides from the middle of the strand

Question 16

What proofreads the DNA for errors

Answer 16

DNA polymerase checks newly inserted base against the template

Question 17

What causes DNA damage after

Answer 17

error bases not corrected, radiation damage, chemical modification
endonuclease removes errors

Question 18

What happens if DNA errors are not corrected

Answer 18

permanent DNA change, damage or mutation

Question 19

What is Polymerase Chain Reaction (PCR)

Answer 19

a fast method of quickly making DNA material to work with targets regions and the exponential increase of DNA molecules

Question 20

What is the Process of PCR

Answer 20

Denaturation-temp increases to seperate DNA strand
Annealing- temp is decreased to allow primers to base pair
Extension-Polymerase extends primer for nascent DNA strand
up to 35 times
2^number of times