Explain why a transferred promoter may be needed
Connect a promoter with transcription of a transferred gene in its host.
A Level; Cambridge International Biology 9700, 2028–2030. This is curriculum teaching, not medical advice or a claim that a treatment is suitable for an individual. Written responses are self-checked
Before you begin
- DNA stores genetic information; genes can be expressed to produce RNA and protein.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why may a promoter be included with a transferred gene?
What you will learn
- Explain the role of a promoter in gene expression
- Explain why a promoter compatible with the host may be transferred
Build the explanation
A promoter is a DNA sequence where RNA polymerase and transcription factors bind to start transcription. A transferred gene may need a promoter recognised by the host’s transcription machinery; without suitable regulatory DNA, the host may not transcribe the coding sequence. The gene and promoter can therefore be transferred together.
Use the evidence carefully
A promoter regulates transcription; it does not code for the protein. A promoter from one organism may not function efficiently in another, so the sequence must be compatible with the host. Expression also depends on other cellular conditions.
Pause and explain
Explain why a eukaryotic promoter may fail in a bacterial host.
Worked example
A coding sequence enters a bacterium but no mRNA is made. What sequence may need to be included?
Show the worked solution
- Transcription must begin.
- A host-recognised promoter is required.
Answer A promoter compatible with the bacterial transcription machinery may need to be transferred with the coding sequence.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
What binds at a promoter to begin transcription?
Give me a hint
Identify the relevant material or technology and explain each step.
Compare my reasoning
- The promoter is a DNA regulatory region.
- RNA polymerase and relevant transcription factors bind.
RNA polymerase and relevant transcription factors bind at the promoter to initiate transcription.
Look for these in your work
- Method identified
- Steps linked to function
A gene is transcribed but its protein is not made. Is a promoter the only possible issue?
Give me a hint
Use the stated example to justify a conclusion.
Compare my reasoning
- Transcription has occurred.
- Translation or later steps may be affected.
No. A promoter supports transcription; translation, mRNA stability or protein processing could still prevent detectable protein.
Look for these in your work
- Evidence interpreted
- Limits stated
Explain why a eukaryotic promoter may fail in a bacterial host.
Give me a hint
Apply the idea to a new application or trade-off.
Compare my reasoning
- The host’s transcription machinery may not recognise it.
- Use a compatible promoter.
The bacterial transcription machinery may not recognise the eukaryotic promoter sequence, so a host-compatible promoter may be required.
Look for these in your work
- Application explained
- Claim appropriately bounded
Common mistakes
- Describing the promoter as part of the protein-coding sequence
- Assuming any promoter works in every host
What can you explain now?
Why may a promoter be included with a transferred gene?
Compare with the explanation
So the host can transcribe the gene
The host must recognise the regulatory sequence.
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Make it stick
What does a promoter do, and why must it match the host?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.