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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 stages:
- Attachment: The virus binds to a specific receptor on the host cell membrane.
- Injection: The viral genetic material is injected into the host cell.
- Replication: The host cell's machinery is hijacked to replicate the viral DNA or RNA.
- Assembly: Newly formed viral proteins and genetic material are assembled into complete virions.
- Lysis and Release: The host cell is lysed, releasing new virions to infect other cells.
Step 2
Step 3
Calculate the number of people infected with measles in 2015. Give your answer in standard form.
Answer
To find the total number of people infected with measles, we can use the formula:
ext{Total Infected} = rac{ ext{Number of Deaths}}{ ext{Death Rate}}
Substituting values:
ext{Total Infected} = rac{134250}{0.0015} = 89500000
In standard form, this is represented as:
Step 4
State two reasons why people might not be immunised against measles.
Answer
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Medical Reasons: Individuals with certain medical conditions or compromised immune systems may be advised against vaccination.
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Misconceptions: Misinformation and fears regarding vaccine safety can lead to reluctance in getting vaccinated.
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 reduces the overall spread of the disease, providing protection even to those who are not immune by decreasing the likelihood of an outbreak.