Distinguish clone genotype from appearance and mutation
Use genetic identity carefully without denying environmental variation.
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 cells, DNA, inherited characteristics and the distinction between growth of an organism and production of offspring.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does genetically identical describe here?
What you will learn
- Separate genetic information and expressed features
- Recognise the limits of a copying model
Distinguish clone genotype from appearance and mutation
| Feature | Meaning |
|---|---|
| Genotype | Inherited genetic information |
| Appearance | Can also be affected by environment |
| Mutation | Can introduce a copying difference |
| Image limit | Similar shape does not directly prove identical DNA |
Separate genetic information and expressed features
A clone is described as genetically identical to its original parent in the normal asexual copying model. Genetic information and the visible expression of a characteristic are related but not identical ideas. Two cuttings from the same plant can grow to different heights if their light, water, mineral supply or other growing conditions differ. That visible difference is not automatically a difference in genotype.
Likewise, a photograph showing similar leaves does not prove that two plants have identical genetic information. Similar appearance may have several causes. A reproductive history showing one-parent vegetative propagation supplies a stronger basis for the expected clone relationship; direct genetic evidence would be needed to test identity at a specified level.
Recognise the limits of a copying model
DNA copying is usually accurate but mutations can occur. A mutation can introduce a genetic difference in a descendant, so the school copying model is not a claim that asexual lineages can never contain variation. The later discussion of population risks concerns the limited genetic diversity typically produced by copying one parent, rather than an absolute absence of any possible mutation.
Use the question’s assumptions before drawing a conclusion. If it states faithful copying with no mutation, descendants share the parent’s genetic information. If it supplies a new DNA change, recognise that exception. Neither different height nor a matching colour on its own establishes the copying mechanism, and a single parent alone also needs careful interpretation when gamete fusion is involved.
Sources for this lesson
Pause and explain
Can a mutation introduce a difference in an asexual lineage?
Worked example
Two cloned cuttings have the same genetic information but different light levels and heights. Explain the difference.
Show the worked solution
- Genotype is held the same in the record.
- Light can alter growth and expressed height.
Answer Different growing conditions can produce different heights despite the same genetic information.
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.
Explain how two cuttings of the same clone can differ in height.
Give me a hint
Separate genotype from growing conditions.
Compare my reasoning
- They share genetic information in the record.
- Environmental conditions can affect growth.
They can share the same genetic information but grow differently because conditions such as light and water differ.
Look for these in your work
- Retain shared genotype
- Name an environmental growth effect
In a stated no-mutation copying model, what genetic relationship is expected after three asexual generations?
Give me a hint
Copying repeats the original source information.
Compare my reasoning
- Each generation copies information from its parent.
- The no-mutation assumption preserves that information.
The descendants are genetically identical to the original parent in the stated no-mutation model.
Look for these in your work
- Use the copying assumption
- Do not invent genetic mixing
A later descendant has a documented DNA copying change. Does this show that all asexual offspring are formed by gamete fusion?
Give me a hint
A mutation and a reproductive mechanism are different facts.
Compare my reasoning
- A copying change can create variation.
- It does not establish fusion of gamete nuclei.
No. The documented mutation introduces a genetic difference but does not establish sexual reproduction or gamete fusion.
Look for these in your work
- Identify mutation as the change
- Keep reproduction mechanism separate
Common mistakes
- Treating all visible differences as mutations.
- Saying asexual reproduction makes mutation impossible.
What can you explain now?
Can a mutation introduce a difference in an asexual lineage?
Compare with the explanation
Yes; a copying change can alter genetic information
The simple clone model does not exclude all mutation.
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Make it stick
Explain why cloned plants may look different and why the basic copying model does not make mutation impossible.
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.