Trace nucleus chromosome DNA and gene in an original model
Structural nesting: nucleus contains chromosomes, chromosome DNA contains gene regions. Enlargements represent existing material; gene presence alone does not show current protein production.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-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.
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 order follows the stated containing and region relationship?
What you will learn
- Follow structural relationships without equating labels
- Locate a protein-coding region within longer DNA
Original teaching model. Counts and records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Containing structure | Nucleus |
| DNA-bearing structure | Chromosome |
| Selected region | Protein-coding gene |
| Evidence limit | An enlarged view does not add a chromosome |
Follow structural relationships without equating labels
Start an information map with the stated animal or plant cell and its nucleus. The nucleus contains chromosomes. Chromosome DNA includes genes; a protein-coding gene is a length of that DNA carrying information for a protein. This is a nested structural relationship, not a chain in which the nucleus changes into a chromosome or the chromosome turns into a gene.
A chromosome can contain many genes, so a single gene label should not be used for the whole chromosome unless the model explicitly marks one region. Likewise, not every piece of DNA on a drawn chromosome should automatically be labelled as one protein-coding gene. The syllabus focuses on the regions used to code for proteins without requiring a detailed map of all non-coding DNA.
Locate a protein-coding region within longer DNA
The original expanded view shows a whole chromosome, a selected DNA stretch and two marked gene regions. The magnified stretch remains part of the original DNA; it is not an extra chromosome added to the cell. This helps interpret enlarged diagrams: the same structure can appear at different scales without multiplying the number of real structures.
When checking labels, ask whether an arrow indicates containment, a selected region or later information use. A bracket around a gene identifies a DNA region, while an information-use arrow toward protein production describes a different relationship. A structural map alone does not prove which genes a particular cell is expressing or which proteins it has already made.
Sources for this lesson
Pause and explain
What does a gene bracket identify?
Worked example
Why does enlarging a gene region not add a chromosome?
Show the worked solution
- Identify the enlargement as another view of existing DNA.
- Separate a view count from a physical structure count.
Answer The enlarged region is part of the same chromosome DNA; drawing it again at a different scale does not create another chromosome.
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.
Write a three-link structural map from nucleus to a protein-coding gene.
Give me a hint
Keep containment separate from information use.
Compare my reasoning
- Place chromosome DNA inside the nucleus.
- Place a gene region on the DNA.
Nucleus contains chromosomes; chromosome DNA contains gene regions; a protein-coding gene carries information for a protein.
Look for these in your work
- Use correct nesting
- Keep the information role
An original diagram redraws one selected DNA stretch beside the chromosome. Explain why counting both drawings as two chromosomes is wrong.
Give me a hint
Compare physical object with enlarged view.
Compare my reasoning
- Identify the second drawing as a selected view.
- Retain the original physical count.
The extra drawing enlarges a region of the existing chromosome; it is not a second chromosome, so the physical count has not doubled.
Look for these in your work
- Identify the enlarged view
- Reject double counting
A structural map labels two genes but has no expression record. Can it show which protein the cell is currently producing?
Give me a hint
Presence and use differ.
Compare my reasoning
- Recognise genes can be present without expression.
- Identify the missing production evidence.
No. Gene regions show available information, but the map does not establish which gene is being used to produce a protein.
Look for these in your work
- Separate presence and expression
- State missing evidence
Common mistakes
- A magnified view is not another physical object.
- Containment does not mean one structure transforms into the next.
What can you explain now?
What does a gene bracket identify?
Compare with the explanation
A selected length of DNA
It marks an information region.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Explain follow structural relationships without equating labels and locate a protein-coding region within longer DNA. 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.