Virus essay mark scheme
Last week’s essay was the following question: “Give an account of the events that occur during the invasion of a host cell by a DNA virus.”
Here’s the mark scheme that we went over in class. As you can see, there are 11 potential marks, of which you could get a maximum of 10.
General background information (must be relevant to viral invasion, not just general information about viruses).
- Viral structure – DNA surrounded by protein capsid or a diagram showing this
- Lacks machinery to replicate – must use host cell
- Once inside, depends on host for ATP, nucleotides and amino acids
Steps of viral invasion:
1. Virus contacts specific host cells and binds
2. Thrusts tail through cell wall
3. Injects DNA into cell
4. Viral DNA replicates using host nucleotides
5. Viral DNA transcribed into viral mRNA
6. mRNA directs protein synthesis (translation) using host amino acids – protein coats
7. Viral DNA is enclosed in protein coat
8. Lysis of host cell
On the whole I was really pleased with the standard of the essays. Most people got at least 6 out of 10, and those scores can be improved by the inclusion of more biological detail. You’ve got to be really specific about including key points and using the correct vocabulary. You will also need to be concise – you won’t have long in the exam to churn out two essays. So don’t be tempted to waffle!
As for this week’s homework, remember that it is to revise for our end-of-topic quiz on Wednesday. This will include viruses, the immune system, and cellular defence in plants. I’m looking for much better scores than last time!
