Nucleic Acids and Gene Expression

Question 1

What does DNA stand for

Answer 1

deoxyribonucleotide acid

Question 2

What is the difference between deoxyribose and ribose

Answer 2

Deoxyribose = -O2

Question 3

Draw the structure of a nucleotide

Answer 3

3 P on the 5’, OH on the 3’, base on the 1’

Question 4

Which bases are purines

Answer 4

A and G

Question 5

Which bases are pyrimidines

Answer 5

C and T

Question 6

Which bases have NH2

Answer 6

A and C

Question 7

which bases have =O

Answer 7

G and T

Question 8

How do bases pair

Answer 8

A and T, C and G

Question 9

What is a nucleoside

Answer 9

A nucleotide without phosphates. Includes adenosine, guanosine, cytidine and thymidine (uridine)

Question 10

What are the structural features of DNA

Answer 10

3’ and 5’ leads to asymmetry
Right hand helix
Major and minor groove

Question 11

How many bonds between base pairs

Answer 11

A-T = 2 H bonds
C-G = 3 H bonds

Question 12

How many bp per turn

Answer 12

10

Question 13

How can DNA be denatured

Answer 13

Lowering salt content or increasing heat

Question 14

Describe the structural organisation of DNA

Answer 14

2nm double helix
11nm Nucleosome (-ve backbone and +ve histone) with 8 core proteins
30nm fibre 
700nm 
1400nm chromosome

Question 15

Which enzymes are involved in DNA replication

Answer 15

Topoisomerase
DNA helicase (needs ATP)
DNA polymerase

Question 16

What are the names of the two strand on the replication fork

Answer 16

Leading and lagging strand

Question 17

What is the process of replication on the lagging strand

Answer 17

1. DNA primase creates and RNA primer which binds to the DNA
2. dNTPs form an Okazaki fragment
3. Ribonuclease removes the previous primer using 5’-3’ exonuclease activity
4. Repair DNA polymerase replaces the primer
5. DNA ligase joins the Okazaki fragments, requiring ATP

Question 18

What are the accessory factors for replication

Answer 18

Single strand binding protein to prevent folding
Sliding clamp to prevent polymerase falling off
3’-5’ exonuclease activity by DNA polymerase to fix mutations

Question 19

How does E. coli replicate

Answer 19

Origin is OriC

Bi-directional with 2 replication forks

Question 20

How do eukaryotes replicate

Answer 20

Multiple replication origins

Bi-directional

Question 21

Describe the cell cyle

Answer 21

G1 - 10hrs
S - DNA synthesis 9 hrs
G2 - 2-4hrs
M - mitosis 1 hrs

Question 22

What is the difference between early and late prophase

Answer 22

early - pairing of chromosomes and crossing over

late- condensing and spindle formation

Question 23

Give examples of nucleoside analogues

Answer 23

Acyclovir - Herpes
AZT - HIV
Cytosine arabinose - Chemo
ddC - HIV

Question 24

What are the types of RNA polymerase

Answer 24

Type 1 - rRNA
Type 2 - mRNA
Type 3 - tRNA

Question 25

What is the promoter region

Answer 25

DNA sequence where the initiation complex forms

Question 26

What are transcription factors

Answer 26

TFs are proteins that regulate genes, acting collectively to bring expression

Question 27

What is the effect of acetylation

Answer 27

``` hyperacetylation = expression Hypoacetylation = repression ```

Question 28

What are some determinants of expression

Answer 28

hormones, heat, stress, voltage, light etc.

Question 29

What are the pre initiation complex and describe its formation

Answer 29

TF II D binds to TATA TF II B and A binds to TF II D RNA polymerase binds to TF II B TF II E, F, H, J binds

Question 30

What is special about TF II D

Answer 30

Causes asymmetrical unwinding of the DNA leading to unidirectionality ] Widens the minor groove contains TBP and TAF

Question 31

What is special about TF II H

Answer 31

further unwinds the DNA helix

Question 32

How is pre-mRNA processed

Answer 32

Removal of intron using snRNPs intron starts with GU and ends in CAG u1 binds to GU while U2,4,5 binds to the chain and U6 binds to CAG breaking of the GU and binding to the branch point (A) DNA ligase joins axons

Question 33

What structure are introns removed as

Answer 33

Lariat

Question 34

What is added to processed mRNA

Answer 34

CAP which protects mRNA and enhances translation | PolyA