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Gregory Mendel used pea plants in plant breeding experiments - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Question 10
Gregory Mendel used pea plants in plant breeding experiments. He discovered the basis of genetic inheritance. (a) (i) Explain why the offspring are all tall. (ii) ... show full transcript
Worked Solution & Example Answer:Gregory Mendel used pea plants in plant breeding experiments - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Step 1
Explain why the offspring are all tall.
Answer
The offspring are all tall because they inherit the dominant allele for the tall phenotype from at least one parent. Since the tall trait is dominant (A), even if the short parent carries a recessive allele (aa), the presence of a tall allele (A) from the other parent will ensure 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 environment optimizes the growth conditions for the pea plants, promoting healthier plants and more successful breeding outcomes.
- The closed environment helps prevent cross-pollination with external plants, ensuring that the genetic crosses are controlled and reliable for the experiment.
Step 3
Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green-coloured peas.
Answer
Using a Punnett square for a cross between two heterozygous pea plants (Aa x Aa):
A | a
---------
A | AA | Aa
---------
a | Aa | aa
From the square, there are 3 dominant (A) and 1 recessive (a) representations. Hence, the percentage probability of producing green-coloured peas (aa) is:
rac{1}{4} imes 100 = 25\%
Step 4
Explain one advantage to pea plants of using sexual reproduction to produce offspring.
Answer
One advantage of sexual reproduction for pea plants is the increased genetic variation among offspring. This variation allows for better adaptability to changing environmental conditions and can lead to increased resilience against diseases.
Step 5
Describe a test to identify fat.
Answer
To identify fat, the ethanol emulsion test can be performed:
- Take a small sample of the pea.
- Crush the sample and mix it with ethanol in a test tube.
- Shake the mixture and then add distilled water. If fat is present, a white emulsion will form, indicating the presence of fat.