Nage 2

Question 1

Explain what is meant by semi conservative replication

Answer 1

In every new segment of DNA, one strand is newly synthesised and another strand is from the parent DNA

Question 2

What enzyme is used to unwind DNA?

Answer 2

Topoisomerase

Question 3

How does the enzyme helical operate

Answer 3

It breaks the hydrogen bonds using ATP

Question 4

Which direction does DNA helicase operate

Answer 4

5’ - 3’

Question 5

What is an oligonucleotide primer and what enzyme is used to synthesise it?

Answer 5

The oligonucleotide primer are small fragments of RNA which starts off Okazaki fragments
They are synthesised by RNA polymerase

Question 6

What is the difference between nucleotides and nucleosides

Answer 6

Nucleosides are not referring to the phosphate groups

Question 7

How can nucleoside analogues be used as drugs

Answer 7

Nucleosides can attach onto replicating viral DNA and as it has no phosphate group, no further polymerisation can occur

Question 8

Where does replication begin in prokaryotes and eukaryotes

Answer 8

The origin of replication

Question 9

What direction is the leading strand going in and what direction is the lagging strand going in

Answer 9

Both are going in the 5’ - 3’ direction

Question 10

What are Okazaki fragments

Answer 10

These are fragments of DNA that are synthesised on the lagging strand in the 5’ - 3’ direction as the strands are anti parallel

Question 11

How are Okazaki fragments added onto a strand of DNA and what enzymes are involved

Answer 11

The oligonucleotide primers form a starting position for further Nucleotides to be added, forming the Okazaki fragments using DNA polymerase. Ligament is used to ligate the fragments together

Question 12

Explain what is meant by exonclease activity

Answer 12

This is when the RNA nucleotides are removed using ribonuclease

Question 13

What is meant by OriC

Answer 13

This is the point of replication

Question 14

Describe replication in mammalian chromosomes

Answer 14

There are several points of replication throughout the chromosome, causing two replication forks to go out in either direction, until the entire chromosome has replicated

Question 15

Name the stages in the cell cycle

Answer 15

Interphase - divided into Gap 1, Synthesis and Gap 2 
Prophase 
Metaphase
Anaphase 
Telophase 
Cytokinesis

Question 16

Explain what happens in interphase

Answer 16

In dividing cells, during interphase, the cell goes into G1 (organelles are synthesised)
Then S (synthesis of DNA)
The G2(DNA is checked}

In cells which are no longer dividing they enter G0