Biochemistry of Nucleic Acids

Question 1

Central Dogma

Answer 1

FLow of genetic information from DNA towards proteins

Question 2

Nucleoside

Answer 2

Base + Sugar

Question 3

Nucleotide = Nucleoside + Phosphate groups

Answer 3

Nucleoside + Phosphate groups

Question 4

DNA & RNA Bases & Pairings

Answer 4

DNA = A-T, G-C
RNA = A-U, G-C
Adenine –> Adenosine
Cytosine –> Cytidine
Guanine –> Guanosine
Thymine –> Thymidine
Uracil –> Uridine

Question 5

Polymerisation

Answer 5

Nucleotide added onto C3 with OH group
Phosphodiester bond is formed between a 3’ OH and 5’ triphosphate
Release of 2 phosphates

Question 6

Nucleic Acid Direction

Answer 6

5’ to 3’
Nucleotides added onto 3’ end

Question 7

DNA Replication

Answer 7

Semi-conservative
DNA polymerase
Require RNA primer
Add onto existing nucleic acids

Question 8

Origins of Replication

Answer 8

Replication starts simulatenously as several points of genome
Bidirectional
Reasonable time of completion

Question 9

Leading strand

Answer 9

Free 3’ end
Nucleotides added onto 3’

Question 10

Lagging strand - Okazaki fragments

Answer 10

Replicated in short segments
Joined by ligase
RNA primers needed (synthesised by primase)

Question 11

Proofreading and Repair

Answer 11

Wrong nucleotides can create mutations
Occurs rarely
DNA Polymerase removes incorrect nucleotides

Question 12

Helicase

Answer 12

Unwind helix and stop it rewinding

Question 13

Replication fork

Answer 13

Contains both a leading and lagging strand