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10 Gregor Mendel used pea plants in plant breeding experiments - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Question 10
10 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 pla... show full transcript
Worked Solution & Example Answer:10 Gregor 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 tallness is a dominant trait in pea plants, meaning it is expressed when at least one dominant allele is present. Since the plants were cross-bred from homozygous tall parents (TT) with short pea plants (tt), all offspring received one tall allele (T) from the tall parent, resulting in all tall plants (Tt).
Step 2
Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.
Answer
- A warm greenhouse environment ensures optimal growth conditions for pea plants, enhancing germination and overall health.
- A closed greenhouse helps to prevent unwanted cross-pollination with other plant species, ensuring controlled breeding experiments.
Step 3
Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green-coloured peas.
Answer
Using the Punnett square for the genetic cross of two heterozygous yellow pea plants (Aa x Aa):
A a
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A | AA | Aa |
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A | AA | Aa |
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From the square, we find: 75% will be AA or Aa (yellow) and 25% will be aa (green). Thus, the percentage probability of offspring producing green-coloured peas is 25%.
Step 4
Explain one advantage to pea plants of using sexual reproduction to produce offspring.
Answer
One advantage of sexual reproduction in pea plants is increased genetic diversity. The combination of genetic material from two parent plants allows for new combinations of traits, which can enhance adaptability and survivability in varying environmental conditions compared to asexual reproduction.
Step 5
Describe a test to identify fat.
Answer
To identify fat, the emulsion test can be conducted. Take a sample of the pea and crush it to obtain a liquid extract. Then add ethanol and shake the mixture. Following that, add an equal volume of water. A milky emulsion indicates the presence of fats.