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Measles is a disease caused by a virus - Edexcel - GCSE Biology - Question 7 - 2019 - Paper 1
Question 7
Measles is a disease caused by a virus. (a) Describe the lytic pathway for a virus. (b) A measles infection can cause inflammation of the brain. Figure 11 shows a ... show full transcript
Worked Solution & Example Answer:Measles is a disease caused by a virus - Edexcel - GCSE Biology - Question 7 - 2019 - Paper 1
Step 1
Describe the lytic pathway for a virus.
Answer
The lytic pathway involves several stages:
- Attachment: The virus binds to the host cell's surface.
- Entry: The viral DNA or RNA is injected into the host cell.
- Replication: The host cell's machinery replicates the viral genetic material and proteins.
- Assembly: New viral particles are assembled within the host cell.
- Lysis: The host cell bursts (lyses), releasing new viruses to infect other cells.
Step 2
Step 3
Calculate the number of people infected with measles in 2015.
Answer
To find the total number of infected individuals, we use the formula:
y = rac{x}{r}
where y is the total infected, x is the deaths (134,250), and r is the death rate (0.0015).
Calculating this gives:
y = rac{134250}{0.0015} = 89650000.
Thus, in standard form, this is approximately people.
Step 4
Step 5
Describe herd immunity.
Answer
Herd immunity occurs when a high percentage of the population becomes immune to a disease, either through vaccination or previous infections. This significantly reduces the spread of the disease, offering protection to those who cannot be vaccinated, such as people with certain health conditions, as the chance of an outbreak is minimized.