Scientists measured the mass of DNA in one cell over a period of 40 hours. The figure shows the results.
Figure: The mass of DNA in one cell over a period of 40 hours

Use the figure to give the length of one complete cell cycle in these cells.
Explain what is happening inside the cell between 8 hours and 14 hours.
Explain why the mass of DNA in one cell falls at 20 hours.
A student looked at the figure and said, 'The two cells made at 20 hours must be genetically different from each other.' Explain why the student is wrong.
63 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.