These eight questions follow the chapter from stage order to variation. Answer each on paper before you open the explanation.
The lessons are in cell division. Record slips in the mistake log and paper-error review.
Questions
1. State the stage of mitosis in which sister chromatids separate. (1 mark)
Answer
Anaphase. The centromeres divide and the chromatids move to opposite poles.
2. A diagram shows chromosomes in a line across the middle of a cell. Name the stage and describe one other feature you would expect. (2 marks)
Answer
Metaphase. Spindle fibres are attached to the centromeres, and the nuclear membrane is absent.
3. A cell with 10 chromosomes divides by mitosis. State the number of chromosomes in each daughter cell and at anaphase. (2 marks)
Answer
Each daughter cell has 10 chromosomes. At anaphase the cell briefly holds 20, because each chromatid is counted as a chromosome.
4. Explain why mitosis gives daughter cells identical to the parent. (2 marks)
Answer
DNA replicates in interphase, and the two copies of each chromosome separate equally in anaphase. Each daughter cell receives one complete copy, so the genetic information is the same.
5. State what separates in meiosis I and what separates in meiosis II. (2 marks)
Answer
Meiosis I separates homologous chromosomes. Meiosis II separates sister chromatids.
6. A cell has 16 chromosomes. State the number in each cell at the end of meiosis II and the number of cells produced. (2 marks)
Answer
Each cell has 8 chromosomes, and 4 cells are produced.
7. A graph shows DNA amount per cell: 6, then 12, then 6, then 3 units. Name the process and explain the falls. (3 marks)
Answer
The process is meiosis.
The rise is DNA replication. The fall from 12 to 6 is the end of meiosis I, and the fall from 6 to 3 is the end of meiosis II. Two falls mean two divisions.
8. A cell has 5 pairs of homologous chromosomes. Calculate the gamete combinations from independent assortment and name one other source of variation. (3 marks)
Answer
Combinations = 2⁵ = 32. Another source is crossing over in prophase I, where sections of chromatids are exchanged, or random fertilisation.
If you got these wrong
- Questions 1 to 4: open sequencing mitosis.
- Questions 5 and 6: open sequencing meiosis.
- Question 7: open comparing chromosome and DNA changes.
- Question 8: open explaining variation from meiosis.
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