Define a protein-coding gene as a length of DNA
Core definition: a gene is a DNA length coding for a protein. It carries information; the DNA does not turn into amino acids. This pathway states the protein-coding syllabus scope explicitly.
Section B16.1 · Chromosomes and genes
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall the nucleus, DNA base pairing, gametes, fertilisation, enzymes, membrane carriers and chemical synapses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which gives the required gene definition?
What you will learn
- Use the syllabus gene definition precisely
- Distinguish coding information from a finished protein
Original teaching model. Counts and records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Material | A length of DNA |
| Role | Codes for a protein |
| Product distinction | Gene is not the protein |
| Scope | Protein-coding syllabus definition |
Use the syllabus gene definition precisely
For this syllabus, define a gene as a length of DNA that codes for a protein. The definition gives both the material and its information role. A gene is not a protein, an amino acid or the whole nucleus. Saying only a gene controls a characteristic misses the DNA region and protein-coding link that this requirement asks learners to state.
The phrase codes for means the DNA carries information used in making the protein; it does not mean DNA physically becomes the protein. DNA bases and the amino acids assembled into a protein are different kinds of building blocks. The Extended sequence later explains the messenger RNA and ribosome links, but those details are not required to give this Core definition.
Distinguish coding information from a finished protein
The syllabus uses a protein-coding gene definition. Wider biology also recognises genes whose products are functional RNA molecules rather than proteins. This broader meaning does not change the requested answer in this pathway, and learners are not asked to memorise a full catalogue of RNA genes. Keep the defined scope rather than claim every DNA region must code for a protein.
The original definition model places a bracket on a DNA length and points to an information role for protein production. The arrow is not a material-conversion arrow. When a question asks for a definition, give the complete concise relationship first, then use an example only if requested. An imagined protein shape cannot by itself reveal an exact gene base sequence.
Sources for this lesson
Pause and explain
What does codes for mean here?
Worked example
What is missing from a gene is a thing controlling a feature?
Show the worked solution
- Name the DNA material.
- Name the protein-coding role.
Answer For this syllabus, a gene is a length of DNA that codes for a protein.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
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.
Give the syllabus definition of a gene.
Give me a hint
Include DNA length and protein coding.
Compare my reasoning
- Name a length of DNA.
- State that it codes for a protein.
A gene is a length of DNA that codes for a protein.
Look for these in your work
- Give the material
- Give the coding role
Correct the statement a gene is a protein stored in the nucleus.
Give me a hint
Distinguish information from product.
Compare my reasoning
- Identify a gene as DNA.
- Identify protein as a product made using information.
A protein-coding gene is a length of DNA, not a stored protein; its information is used to make a protein.
Look for these in your work
- Correct the material
- Retain information use
A diagram says a DNA gene is used up and converted into amino acids. Evaluate.
Give me a hint
Information use is not material conversion.
Compare my reasoning
- Retain the gene as DNA.
- Identify amino acids as different building blocks.
The claim is wrong: the gene provides information and remains DNA; amino acids are assembled into a protein rather than being converted from the gene.
Look for these in your work
- Reject DNA consumption
- Distinguish the protein material
Common mistakes
- DNA is not converted into amino acids.
- Use the specified protein-coding scope.
What can you explain now?
What does codes for mean here?
Compare with the explanation
Carries information used to make a protein
It is an information relationship.
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Make it stick
Explain use the syllabus gene definition precisely and distinguish coding information from a finished protein. Use the stated cell, chromosome sets and information pathway before opening the solutions.
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.