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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 consists of several key steps:
- Attachment: The virus attaches to the host cell by binding to specific receptor sites.
- Penetration: The viral genetic material is injected or enters the host cell, often encapsulated in a protein coat.
- Replication: The host's cellular machinery is hijacked to replicate the viral genome and produce viral proteins.
- Assembly: Newly formed viral components are assembled into complete viral particles.
- Lysis and Release: The host cell bursts (lysis), releasing new viruses to infect other cells.
Step 2
Step 3
Calculate the number of people infected with measles in 2015.
Answer
To calculate the number of people infected with measles, we can use the formula:
ext{Number of Infected} = rac{ ext{Number of Deaths}}{ ext{Death Rate}} imes 100
Substituting the values:
ext{Number of Infected} = rac{134250}{0.0015} = 89500000
In standard form, this is:
.
Step 4
Step 5
Describe herd immunity.
Answer
Herd immunity occurs when a significant portion of a population becomes immune to a disease, either through vaccination or previous infections. This immunity helps protect those who are not immune by reducing the likelihood of disease transmission. As a result, even individuals who cannot be vaccinated (e.g., infants or those with certain health issues) are less likely to contract the disease because the spread is minimized within the community.