Complete Figure 7 to show the chromosome content of the cells that would result from a normal meiotic division of the diploid parent cell shown in Figure 6 - AQA - A-Level Biology - Question 6 - 2018 - Paper 1
Question 6
Complete Figure 7 to show the chromosome content of the cells that would result from a normal meiotic division of the diploid parent cell shown in Figure 6.
If two ... show full transcript
Worked Solution & Example Answer:Complete Figure 7 to show the chromosome content of the cells that would result from a normal meiotic division of the diploid parent cell shown in Figure 6 - AQA - A-Level Biology - Question 6 - 2018 - Paper 1
Step 1
Complete Figure 7 to show the chromosome content of the cells that would result from a normal meiotic division
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Answer
After the first division of meiosis, the chromosome content would be:
Cell 1: 1 long and 1 short chromosome (each made up of 2 chromatids).
Cell 2: 1 long and 1 short chromosome (each made up of 2 chromatids).
After the second division of meiosis, the chromosome content would be four daughter cells:
Cell 1: 1 long chromosome.
Cell 2: 1 long chromosome.
Cell 3: 1 short chromosome.
Cell 4: 1 short chromosome.
Step 2
Complete Table 3 to show the expected number of plants that did not produce 2n gametes and the expected number of plants that did produce 2n gametes after 1 cycle.
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Breeding Cycle 0:
Observed: 14 produced 2n gametes
Expected: 14 (2n gametes); therefore, 0 did not produce 2n gametes.
Breeding Cycle 1:
Observed: 42 produced 2n gametes.
Expected: 42 (2n gametes); thus 0 did not produce 2n gametes.
Breeding Cycle 2:
Observed: 44 produced 2n gametes.
Expected: 44 (2n gametes); therefore, 0 did not produce 2n gametes.
Breeding Cycle 3:
Observed: 56 produced 2n gametes.
Expected: 56 (2n gametes); thus, 0 did not produce 2n gametes.
Step 3
What does this result suggest about the difference between the observed and expected results and what can the scientists therefore conclude?
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Answer
The calculated chi-squared value of 350 significantly exceeds the critical value of 3.841. This suggests that there is a highly significant difference between the observed and expected results, leading to the rejection of the null hypothesis. The scientists can conclude that the proportion of plants producing 2n gametes does change from one breeding cycle to the next.
Step 4
Use your knowledge of directional selection to explain the results shown in Table 3.
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Directional selection may have occurred in the red clover plants as those producing 2n gametes were favored. Over successive breeding cycles, plants that produced the trait for 2n gametes became more prevalent. Consequently, the frequency of alleles associated with the production of 2n gametes likely increased within the population.