Cabbage (Brassica oleracea) and radish (Raphanus sativus) both have a diploid number of 18 - VCE - SSCE Biology - Question 6 - 2006 - Paper 1
Question 6
Cabbage (Brassica oleracea) and radish (Raphanus sativus) both have a diploid number of 18. However, they do not naturally hybridise with each other.
a. How many ch... show full transcript
Worked Solution & Example Answer:Cabbage (Brassica oleracea) and radish (Raphanus sativus) both have a diploid number of 18 - VCE - SSCE Biology - Question 6 - 2006 - Paper 1
Step 1
How many chromosomes would be expected in the gametes of the cabbage?
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Answer
The gametes of cabbage, which has a diploid number of 18, would contain half of this number due to meiosis. Therefore, the expected number of chromosomes in the gametes of the cabbage would be:
rac{18}{2} = 9.
Step 2
What would be the diploid number of the hybrid?
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Answer
The diploid number of the hybrid between cabbage and radish would be the sum of the diploid numbers of both parent species. Since cabbage and radish both have a diploid number of 18, the hybrid would have:
18+18=36 chromosomes.
Step 3
Explain why the hybrid of the cabbage and radish is sterile.
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Answer
The hybrid is sterile because the chromosomes from the cabbage and radish do not form homologous pairs during meiosis. This inability to pair prevents proper segregation of chromosomes, leading to the production of non-viable gametes.
Step 4
What term is used to describe cells with more than two sets of chromosomes?
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Cells with more than two sets of chromosomes are referred to as polyploid.
Step 5
Explain, with reference to the events of meiosis, why the new plants are fertile.
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Answer
The new plants become fertile through a spontaneous event that doubles the chromosome number to a tetraploid state. In meiosis, this allows the chromosomes to line up correctly in homologous pairs, resulting in viable gametes. As a result, the new plants can reproduce and produce fertile offspring.
