rev

Question 1

What are the characteristics of viruses?

Answer 1

1. Viral DNA
2. Capsid
   - Protects viral genome
   - Aids in attachment & penetration of host cell
   - viral enzymes
3. Viral envelope
   - From host CSM contains glycoproteins eg. HA NA gp41 gp120
   Complementary in shape to receptors on host cell

Question 2

Describe Generalised Transduction

Answer 2

For lytic life cycle virulent phage eg. T4
1. (Adsorption) T4 tail fibre complementary in shape to specific receptor site in CSM. virulent phage attaches & infects host cell lysozymes released degrade peptidoglycan cell wall.
2. bacterial DNA degraded by phage enzymes
3. (Assembly) of phage particles viral DNA packaged into capsid
4. Bacterial DNA accidentally RANDOMLY packaged into capsid -> GENERALISED TRANSDUCING PHAGE
5. infects another bact. host, injects bact DNA from previous host
6. Homologous recombination -> bact. DNA can replace homologous region recombinant DNA from 2 bact. cells

Packaging error

Question 3

Describe specialised transduction

Answer 3

For lysogenic temperate phage eg. Lambda
1. Temperate phage infects host cell, integrates viral DNA into bacterial chromosome -> prophage
2. env. lysogenic -> lytic prophage excised
3. Excision error, adjacent bacterial genes packaged into specialised transducing phage particle
4. infects other bact, bacterial DNA from previous host replaces homologous region of new host cell via homologous recombination
5. Recombinant DNA from 2 bact cells.

Excision error

Question 4

Describe features of influenza

Answer 4

ON SURFACE
Contains haemagglutinin -> bind to neuraminic acid containing receptor sites on host CSM
& neuraminidase glycoproteins cleaves neuraminic acid residue on host surface
(targets for antiviral drugs, antibodies bind to HA& NA)

GENOME
8 segemnts of (-) ssRNA around nucleocapsid proteins
Contains enzyme RNA dep RNA pol.
need to synthesise (+) strand for translation + synthesise more

Question 5

How does influenza repro

Answer 5

1. HA on viral envelope recognise & bind to receptors on CSM of host cell (epithelial)
2. Influenza virus enters via RME, host CSM forms endosome arnd virus
3. Endosome -> acidic, triggers conform. change, fusion of viral envelope & endosomal membrane
4. M2 ion channel (acidifies + uncoats nucleocapsids into cytosol)
5. Cellular enzymes digest nucleocapsid proteins -> viral RNA migrates to nucleus.

Question 6

Synthesis of influenza

Question 7

Assembly & release of influenza

Question 8

Trp Operon

Answer 8

Negative control repressible operon
switches on when tryptophan absent
Tryptophan available -> corepressor
changes conformation of repressor -> binds to inactive repressor, activates it
Active repressor binds to promoter, RNA pol cannot bind to promoter, no transcription of trp
Anabolic

Question 10

Transformation

Answer 10

DNA of donor bacterium lysed, fragmented and released in environment.
Fragment taken up by competent bacterium
DNA binding protein on outer surface of cell wall
HOMOLOGOUS RECOMBINATION donor DNA incorporated in recipient cell