A conservation charity wants to preserve an endangered orchid species. Scientists have taken small pieces of tissue from the leaves of a healthy orchid and used them to grow thousands of new orchid plants. Explain how this tissue culture process produces genetically identical plants, and explain why maintaining genetic variation in the wild population is still important for the survival of the species.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
An endangered orchid species has fewer than 200 plants remaining in the wild. The charity hopes to reintroduce laboratory-grown plants into the orchid's natural habitat.
Model answer (5 marks)
The tissue is taken from a single parent plant, so only one genotype is involved.
The cells are grown in vitro without fertilisation, so no gamete fusion occurs and no new allele combinations are created.
The new cells divide by mitosis, which copies the DNA exactly, producing clones that have the same genotype as the parent.
Because all reintroduced plants are genetically identical, the population will have very low genetic variation.
Low variation means the wild population will be less able to adapt to environmental changes, new diseases or pests, and a single threat could wipe out the whole group.
The cells are grown in vitro without fertilisation, so no gamete fusion occurs and no new allele combinations are created.
The new cells divide by mitosis, which copies the DNA exactly, producing clones that have the same genotype as the parent.
Because all reintroduced plants are genetically identical, the population will have very low genetic variation.
Low variation means the wild population will be less able to adapt to environmental changes, new diseases or pests, and a single threat could wipe out the whole group.
Examiner tips
- Use the terms asexual reproduction, mitosis, and genetic variation; link each point to the marks scheme.
- Show the logical sequence: single parent → no fertilisation → mitotic cloning → identical genotype → low variation → vulnerability.
Common mistakes
- Confusing mitosis with meiosis; students say ‘gamete fusion’ instead of ‘no fertilisation’.
- Failing to explain why low variation is a problem for survival.
Mark scheme (5 marks)
- The tissue cells are taken from a single parent plant / only one parent is involved (asexual reproduction)
- No fertilisation / fusion of gametes occurs, so no new combination of alleles is introduced
- The new cells are produced by mitosis / cell division that copies the DNA exactly, so all offspring have the same genotype as the parent
- Low genetic variation means the wild population may not be able to adapt to changes in the environment / new diseases / pests through natural selection
- If all reintroduced plants are genetically identical, a single disease or environmental change could cause extinction of the whole population
Key terms in this question
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →