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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 tall phenotype (A) is dominant over the short phenotype (a). Since both parent plants used in the cross were heterozygous (Aa), they inherited one tall allele from each parent, leading to all offspring expressing the tall phenotype.
Step 2
Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.
Answer
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To provide optimal growth conditions, ensuring that the plants could grow in a controlled environment, free from external variables.
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To reduce the chances of disease and pests, as maintaining a closed environment helps limit exposure to pathogens.
Step 3
Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green-coloured peas.
Answer
In the cross of two heterozygous plants (Aa x Aa), the Punnett square shows:
A a
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A | AA | Aa |
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a | Aa | aa |
From this, we see that only 1 out of 4 offspring (aa) will produce green-coloured peas. Thus, the percentage probability is 25%.
Step 4