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Gregor Mendel used pea plants in plant breeding experiments - Edexcel - GCSE Biology - Question 4 - 2020 - Paper 1
Question 4
Gregor Mendel used pea plants in plant breeding experiments. He discovered the basis of genetic inheritance. (a) He cross-bred tall pea plants with short pea plants... show full transcript
Worked Solution & Example Answer:Gregor Mendel used pea plants in plant breeding experiments - Edexcel - GCSE Biology - Question 4 - 2020 - Paper 1
Step 1
Explain why the offspring are all tall.
Answer
The offspring are all tall because the allele for tallness is dominant over the allele for shortness. Since the parent plants are heterozygous, they possess one tall allele (A) and one short allele (a). The presence of at least one dominant tall allele in the offspring ensures that all of them display the tall phenotype.
Step 2
Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.
Answer
- Providing ideal growth conditions allows for optimal development and reduces stress on the plants.
- Growing them in a controlled environment minimizes the risk of disease and pests, thereby promoting a healthy growth environment.
Step 3
Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green-coloured peas.
Answer
The Punnett square for the cross between two heterozygous plants (Aa x Aa) would be:
A | a
-------
A | AA | Aa
-------
| Aa | aa
From this square, we see that 1 out of 4 offspring (aa) will produce green-coloured peas. Therefore, the percentage probability is 25%.
Step 4