A plant cutting is taken from a parent plant and placed in water until roots form. New cells are produced in the cutting by mitosis. Explain why it is important that the new cells produced in the cutting are genetically identical to the parent plant cells, and describe the process that ensures this happens.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A gardener takes a cutting from a rose bush by removing a small stem section. The cutting is placed in water and, after several weeks, new roots and shoots form as the cutting grows into a new plant.
Model answer (5 marks)
1. The new plant must have the same traits as the parent, so the cells must be genetically identical.
2. Before division the DNA is copied (replicated) so each chromosome has a sister chromatid.
3. During mitosis the sister chromatids are pulled to opposite poles of the cell.
4. The cell then divides, forming two daughter cells.
5. Each daughter cell contains the same number of chromosomes and the same genetic information as the parent cell.
2. Before division the DNA is copied (replicated) so each chromosome has a sister chromatid.
3. During mitosis the sister chromatids are pulled to opposite poles of the cell.
4. The cell then divides, forming two daughter cells.
5. Each daughter cell contains the same number of chromosomes and the same genetic information as the parent cell.
Examiner tips
- Use the word ‘mitosis’ and mention DNA replication; link identical genetics to plant identity.
- Show the sequence: replication → chromosome alignment → separation → cell division → identical daughters.
Common mistakes
- Confusing meiosis with mitosis; describing genetic variation instead of identity.
- Omitting the step of DNA replication or the equal distribution of chromosomes.
Mark scheme (5 marks)
- New cells must be genetically identical to the parent plant so that the cutting grows into the correct type of plant / has the same characteristics as the parent
- Before division, the DNA / chromosomes are copied / replicated so there are two copies of each chromosome
- The copies of chromosomes / DNA are pulled to opposite ends / poles of the cell
- The cell then divides / the nucleus divides to produce two daughter cells
- Each daughter cell contains the same number of chromosomes / same genetic information as the parent cell
Key terms in this question
mitosis · genetically identical
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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