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Figure 6 shows a faulty form of meiosis that can occur in some plants - AQA - A-Level Biology - Question 6 - 2018 - Paper 1
Question 6
Figure 6 shows a faulty form of meiosis that can occur in some plants. Figure 6 Chromosome content of a diploid parent cell 1st division of meiosis ... show full transcript
Worked Solution & Example Answer:Figure 6 shows a faulty form of meiosis that can occur in some plants - AQA - A-Level Biology - Question 6 - 2018 - Paper 1
Step 1
Complete Figure 7 to show the chromosome content after 1st division of meiosis
Answer
After the first division of meiosis, the chromosome content in each daughter cell should be represented as follows:
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Two circles, each showing the haploid (1n) chromosome content, which is the result of the first meiotic division. This indicates that there are two cells, each containing one long and one short chromosome, denoted as:
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1 long chromosome
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1 short chromosome
Step 2
Complete Table 3 to show the expected number of plants that did not produce 2n gametes after 1 cycle.
Answer
Based on the observed frequency, calculate the expected numbers for the plants:
- Breeding cycle 1: Total observed 56 - Observed producing 2n: 14
- Expected: 56 - 14 = 42 plants (did not produce 2n gametes)
- Breeding cycle 2: Total observed 56 - Observed producing 2n: 44
- Expected: 56 - 44 = 12 plants (did not produce 2n gametes)
- Breeding cycle 3: Total observed 56 - Observed producing 2n: 36
- Expected: 56 - 36 = 20 plants (did not produce 2n gametes)
Step 3
What does this result suggest about the difference between the observed and expected results?
Answer
The calculated chi-squared value exceeds the critical value at P<0.05. This indicates that the differences between observed and expected results are statistically significant; thus, we can reject the null hypothesis. This suggests that the proportion of plants that produce 2n gametes has changed from one breeding cycle to the next.
Step 4
Use your knowledge of directional selection to explain the results shown in Table 3.
Answer
Directional selection may have occurred favoring traits that increase the production of 2n gametes in red clover plants. Over time, individuals that produced 2n gametes may have had a reproductive advantage, leading to an increase in their frequency in subsequent breeding cycles. This change indicates evolutionary pressure affecting the gamete production traits in the population.