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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 tall plants (heterozygous) possess one allele for tallness (A) and one for shortness (a), the presence of the dominant allele (A) ensures that all offspring exhibit the tall phenotype.
Step 2
Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.
Answer
- A warm greenhouse provides optimal growth conditions, reducing stress from environmental fluctuations.
- A closed environment prevents unwanted pollination, ensuring controlled breeding and genetic consistency.
Step 3
Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green-coloured peas.
Answer
Utilizing a Punnett square:
A a
A | AA Aa
|
--------------
a | Aa aa
|
The resulting genotypes are 25% AA (yellow), 50% Aa (yellow), and 25% aa (green). Therefore, the percentage probability that this cross will have offspring that produce green-coloured peas is 25%.
Step 4