Lecture 1

Question 1

Which direction is DNA read?

Answer 1

3’ to 5’

Question 2

Structure of a nucleotide?

Answer 2

Nitrogenous Bases :
Adenosine, cytosine, guanine and thymine (uracil instead of thymine in RNA)
- A and G are purines (2 rings)
- C and T are pyrimidines (3 rings)
- AT GC pair

Sugar group :
Deoxyribose

Phosphate group

Phosphodiester bond :
Condensation reaction forms a phosphodiester bond between hydroxyl group on 1 nucleotide and the phosphate group on the other.

Question 3

Visualisation of phosphodiester bond

Answer 3

Question 4

What are the stages of the cell cycle?

Answer 4

2 main phases, interphase and mitotic (M) phase.

Interphase :
- G1
- S
- G2

M phase :
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis

Question 5

What is involved in interphase

Answer 5

Question 6

Phases of Mitosis

Answer 6

Question 7

What are the 3 steps of DNA replication

Answer 7

1. Initiation
2. Elongation
3. Termination

Question 8

Enzyme activity in DNA replication

Answer 8

Helicase :
- Unwinds double helical DNA

Primase :
- Adds ribonucleotide triphosphates to synthesise an RNA primer
- It binds to the initiation point of a 3’ to 5’ parent chain

Polymerase :
- 5’ to 3’
- Adds 1000 bases per second to growing chain
- Requires a template strand and primer to start
- Proof reads

Exonucleases :
- Remove nucleotides from end of DNA strand

Ligase :
- Joins ends of single DNA strands by making new phosphate bonds

Gyrase :
- Relaxes supercoils produced when molecule is twisted during replication

Telomerase :
- Uses short RNA template to add short DNA repeats to ends of linear chromosomes when primers are removed

Question 9

Different types of polymerase

Answer 9