A fruit grower wants to produce large numbers of a new variety of strawberry plant that produces unusually large, sweet fruits. The grower decides to use tissue culture to clone the new variety. Explain how tissue culture produces genetically identical plants and why this is useful to the fruit grower.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Tissue culture is a cloning technique used in horticulture. Small groups of cells are taken from a parent plant and grown into new plants under carefully controlled laboratory conditions.
Model answer (5 marks)
1. A small number of cells (explants) are taken from the parent strawberry plant.
2. The explants are placed on a sterile growth medium that contains nutrients and plant hormones.
3. The cells divide by mitosis, forming new plantlets.
4. Because mitosis copies the DNA exactly and no sexual reproduction occurs, the new plantlets are genetically identical to the parent plant.
5. This is useful to the grower because every clone will have the desirable trait of large, sweet fruits and large numbers can be produced quickly.
2. The explants are placed on a sterile growth medium that contains nutrients and plant hormones.
3. The cells divide by mitosis, forming new plantlets.
4. Because mitosis copies the DNA exactly and no sexual reproduction occurs, the new plantlets are genetically identical to the parent plant.
5. This is useful to the grower because every clone will have the desirable trait of large, sweet fruits and large numbers can be produced quickly.
Examiner tips
- Use the word "mitosis" to show the process of cell division. Mention that the growth medium contains hormones to stimulate growth. Explain that genetic identity comes from mitosis and the absence of meiosis. Highlight the benefit: uniformity of fruit quality and rapid multiplication.
Common mistakes
- Confusing mitosis with meiosis or sexual reproduction. Forgetting to mention the sterile growth medium or plant hormones. Failing to state that the clones are genetically identical to the parent plant.
Mark scheme (5 marks)
- Small number of cells (explant) taken from the parent strawberry plant
- Cells are grown on a growth medium (containing nutrients / hormones) in sterile conditions
- Cells divide by mitosis to produce new plants
- The new plants are genetically identical to the parent plant because mitosis copies DNA exactly / no sexual reproduction occurs
- This is useful because all plants will have the desirable phenotype (large, sweet fruits) and large numbers can be produced quickly
Key terms in this question
tissue culture · genetically identical
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →