Cells are regularly lost from the lining of a person's mouth and are replaced. The cell cycle in this tissue takes 18 hours. A scientist examines a sample of cells.
| Cells examined | Cells in mitosis |
|---|---|
| 180 | 15 |
In a second investigation, a chemical is applied to a small area of the lining. The chemical only prevents cell fibres from pulling the copied chromosomes to opposite ends of a cell.
| Time | Mean number of lining cells in the same-sized area |
|---|---|
| Before the chemical is applied | 260 |
| 5 days after the chemical is applied | 195 |
Calculate the estimated time a cell spends in mitosis. Give your answer in hours.
Explain how the results of the second investigation show that disrupting mitosis affected the replacement of cells in the lining.
The chemical is removed. A cell from the lining has 46 chromosomes before its DNA is copied. Give the number of chromosomes in each daughter cell after the cell completes the cell cycle.
104 exam-style questions on AQA GCSE Biology 1.2 Cell division, covering 1.2.1 Chromosomes, 1.2.2 Mitosis and the cell cycle, and 1.2.3 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.