2.2 Viruses

Question 1

give two features of DNA virus and examples

Answer 1

contains DNA as genetic material
contains a protein coat (capsid)
e.g smallpox, bacteriophage

Question 2

describe the lysogenic pathway

Answer 2

1. bacteriophage attaches to bacterium
2. phage DNA is injected into host - synthesis of viral enzymes occur
3. viral DNA is incorporated into host cell DNA
4. viral DNA is replicated each time the bacterium divides, without causing the damage

Question 3

describe the lytic pathway

Answer 3

1. phage DNA inactivates the host cell’s DNA and takes over cell biochemistry
2. phage DNA is replicated
3. new phage particles make new protein coats around phage DNA. enzyme lysosome is made or released
4. lysis occurs- the bacterial cell bursts, due to lysosome action, releasing up to 1000 phages to infect other bacteria

Question 4

give two features of RNA viruses

Answer 4

single-stranded RNA genetic material
protein coat (capsid)

Question 5

what is the difference between positive ssRNA and negative ssRNA

Answer 5

positive ssRNA
-can be directly transcribed into a viral protein
e.g TMV, SARS, Polio
negative ssRNA
-transcribed into sense then translated into a viral protein
e.g measles, rebella

Question 6

describe how positive ssRNA can be turned into new viral particles

Answer 6

RNA is a sense strand which acts as mRNA
it is translated using host’s ribosomes into viral proteins
viral proteins make new viral particles

Question 7

describe how negative ssRNA can be turned into new viral particles

Answer 7

RNA is an antisense strand that cant act as mRNA
it is transcribed into sense RNA which can act as mRNA
it is then translated into viral proteins which turn into new viral particles

Question 8

give two features of RNA retroviruses and give examples

Answer 8

protein coat (capsid)
single strand of RNA
e.g HIV, leukaemia

Question 9

describe process of turning RNA into new viral particles

Answer 9

1. RNA cannot be directly transcribed so using enzyme reverse transcriptase it is turned into DNA
2. DNA is transcribed into mRNA
3. mRNA is translated into viral proteins and thus viral particles

Question 10

what do all viruses have in common

Answer 10

they all have genetic material and a protein coat

Question 11

how can viruses be spread

Answer 11

saliva droplets
infected blood
infected faeces
contact from infected individual

Question 12

what does virulent mean

Answer 12

pathogen that spreads easily

Question 13

how can you treat viral infections

Answer 13

antiviral drugs that target viral replication

Question 14

how do antivirals work

Answer 14

targeting the receptors by which viruses recognise the host cell
targeting the enzymes that translate or replicate the viral DNA or RNA
inhibiting the protease enzymes that allow viruses to bud from hosts

Question 15

how can you prevent the transmission of viral particles

Answer 15

hygiene
masks
quarantine
reduced contact
sterilisation
diet changes

Question 16

how can you control the spread of disease

Answer 16

rapid identification
nursing in isolation
prevention of transmission
sterilisation 
protective clothing by healthcare workers

Question 17

describe vaccinations

Answer 17

provide immunity by stimulating a primary immune response

Question 18

describe the timeline for drug development

Answer 18

preclinical research
-discover and early screening of compound
-large scale synthesis
-animal testing
clinical studies
-phase 1-few participants to assess the safety
-phase 2- 100+ participants-study efficacy
-phase 3- 1000+ participants-study safety, efficacy and dosing
approval
-post-market observation and watch for side effects

Question 19

what is a treatment for Ebola

Answer 19

ZMapp

experimental drug produced after studies of people who survived Ebola in previous outbreaks.