Gregor Mendel carried out crosses with pea plants and observed patterns in the characteristics of offspring. Describe the contribution Mendel made to our understanding of genetic inheritance, and explain why his work was not immediately accepted by other scientists.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Mendel crossed pea plants with contrasting traits such as flower colour or seed shape and recorded the traits of the offspring.
He observed regular ratios in the offspring, showing that traits were inherited as discrete units – dominant and recessive alleles – rather than blending.
His work was not accepted immediately because other scientists could not replicate his results and the scientific community did not yet have the tools or theoretical framework to understand his findings.
Only in the 20th century, when new microscopes and genetic theory allowed verification of his work, did it become recognised and accepted.
He observed regular ratios in the offspring, showing that traits were inherited as discrete units – dominant and recessive alleles – rather than blending.
His work was not accepted immediately because other scientists could not replicate his results and the scientific community did not yet have the tools or theoretical framework to understand his findings.
Only in the 20th century, when new microscopes and genetic theory allowed verification of his work, did it become recognised and accepted.
Examiner tips
- Use the words ‘crossed’, ‘recorded’, ‘dominant’ and ‘recessive’ – these are key terms.
- Explain the lack of acceptance in terms of replication and lack of technology.
- Mention the later verification in the 20th century to show full understanding.
- Keep the answer concise – 4 points only.
Common mistakes
- Mixing up Mendel’s work with the blending inheritance model.
- Failing to mention the need for replication or technology as reasons for initial rejection.
- Using vague terms like ‘good work’ instead of specific scientific reasons.
Mark scheme (4 marks)
- Mendel crossed pea plants with different characteristics (such as flower colour or seed shape) and recorded the characteristics of the offspring.
- He found a correlation in characteristics between parents and offspring, identifying dominant and recessive alleles / traits.
- His work was not accepted at first because other scientists did not verify or replicate his results at the time / his findings were criticised.
- It was not until the 20th century, when other scientists verified his results (and better microscopes / technology became available), that his work became recognised / accepted.
Key terms in this question
characteristics · genetic inheritance
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