A-Level AQA Biology Populations: Figure 6 shows a faulty form of

Question

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

Two daughter cells do not develop

Chromosome content after 1st division

2nd division of meiosis

Chromosome content of the two daughter cells that develop as gametes

Diploid (2n)

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.

Figure 7

Chromosome content after 1st division of meiosis

2nd division of meiosis

Chromosome content of the four daughter cells.

If two diploid (2n) gametes fuse at fertilisation, it can result in the growth of a tetraploid plant which has 4 copies of each chromosome.

Red clover is a plant grown to produce cattle feed. Tetraploid red clover plants produce a higher yield than diploid red clover plants.

Whether a red clover plant produces 2n gametes is genetically controlled.

Scientists investigated the possibility of breeding red clover plants that only produced 2n gametes.

In breeding cycle 0, they grew red clover plants and identified plants that produced 2n gametes.

In breeding cycle 1, they used the plants producing 2n gametes to produce offspring.

In breeding cycles 2 and 3, they identified plants producing 2n gametes and used these to produce offspring.

Their results are shown in Table 3.

Table 3

Observed | Expected
Number of plants that produced 2n gametes

Breeding cycle  |  | 
1 | 14 | 42 |  
2 | 22 | 44 |  
3 |  0 | 56 |

The scientists used the following null hypothesis.

‘The proportion of plants that produce 2n gametes will not change from one breeding cycle to the next.’

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.

The scientists tested their null hypothesis using the chi-squared statistical test.

After 1 cycle their calculated chi-squared value was 350

The critical value at P<0.05 is 3.841

What does this result suggest about the difference between the observed and expected results and what can the scientists therefore conclude?

Use your knowledge of directional selection to explain the results shown in Table 3.

Figure 6 shows a faulty form of meiosis that can occur in some plants - AQA - A-Level Biology - Question 6 - 2018 - Paper 1

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

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.

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.

What does this result suggest about the difference between the observed and expected results and what can the scientists therefore conclude?

Use your knowledge of directional selection to explain the results shown in Table 3.

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