Explain different cell functions through selective gene expression
Most body cells share genes but can express different subsets to make different needed proteins. Gene presence is distinct from current use; nucleus-free cell exceptions and variable expression remain explicit.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
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
How can cells with the same supplied genes have different functions?
What you will learn
- Separate genes present from genes currently used
- Connect required proteins with specialised cell function
Original teaching model. Counts and records are stipulated; drawings are schematic.
| Feature | Meaning |
|---|---|
| Available information | Shared supplied gene set |
| Selective use | Different genes expressed |
| Product | Proteins needed for cell function |
| Qualifier | Most body cells, not every cell without exception |
Separate genes present from genes currently used
Most body cells in an organism contain the same genes, yet different cell types have different functions. Many genes present in a particular cell are not expressed there because the cell makes the particular proteins it needs. Gene expression means using gene information to produce its functional product; in this protein-coding pathway the relevant product is a protein.
A cell making enzyme E and another cell making receptor R need not have completely different DNA gene collections. Their different production can arise through different genes being expressed. Selective use of information is not the same as deleting every unused gene. This helps explain specialisation while keeping the distinction between available information and current function.
Connect required proteins with specialised cell function
The phrase most body cells matters. A mature mammalian red blood cell lacks a nucleus, so do not make an exception-free claim that every body cell has an identical nuclear gene collection. The stated model compares nucleated body cells with the same supplied gene set; it does not attempt to describe every mutation, specialised DNA change or cell exception.
The original expression switch is a teaching model showing genes present and products currently made as separate rows. It does not imply expression is always a simple permanent on/off state; amounts and conditions can vary. A missing product observation also does not, by itself, prove the DNA gene is absent or that the protein was never made earlier.
Pause and explain
What is wrong with every body cell always has the same nuclear genes?
Worked example
Why can two nucleated cells with the same supplied genes make different proteins?
Show the worked solution
- Retain the shared gene collection.
- Explain different genes being expressed for cell needs.
Answer They can express different genes and make different required proteins even though the supplied DNA gene collection is the same.
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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.
Explain different protein production in two nucleated cells with the same supplied gene set.
Give me a hint
Use selective expression and different protein needs.
Compare my reasoning
- Keep the shared DNA information.
- Use different genes to make the needed proteins.
The cells can contain the same genes but express different subsets, producing the proteins needed for their different functions.
Look for these in your work
- Retain gene presence
- Explain selective use
A gene is present but not currently expressed in a stipulated cell. Has it necessarily been deleted?
Give me a hint
Presence and use are different.
Compare my reasoning
- Retain the supplied DNA gene presence.
- Distinguish non-expression from removal.
No. The gene remains present in the supplied DNA record but is not currently being used in that cell; non-expression is not deletion.
Look for these in your work
- Keep the given presence
- Separate use and removal
Evaluate an all-body-cells statement using a mature mammalian red blood cell.
Give me a hint
The syllabus says most, not every.
Compare my reasoning
- Identify the mature cell’s lack of a nucleus.
- Reject the exception-free nuclear-gene claim.
A mature mammalian red blood cell has no nucleus, so an exception-free claim about every body cell’s identical nuclear genes is inaccurate; the syllabus uses most body cells.
Look for these in your work
- Identify the exception
- Retain the correct qualifier
Common mistakes
- Unused information is not necessarily deleted.
- Most body cells is not an exception-free every-cell statement.
What can you explain now?
What is wrong with every body cell always has the same nuclear genes?
Compare with the explanation
Most body cells allows exceptions such as nucleus-free mature mammalian red blood cells
The qualifier matters.
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Make it stick
Explain separate genes present from genes currently used and connect required proteins with specialised cell function. 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.