Mitosis and the cell cycleEdexcel International A Level Biology: Mind map

Exam questions on Mitosis and the cell cycle

1. A student prepares a squash from the tip of an onion root and views it under a light microscope. She sees many cells in different stages of the cell cycle.
   The student cut only the first 1–2 mm from the root tip rather than a section from the middle of the root. Explain why.2 marks
2. A student counted the cells in several fields of view of a stained root tip squash. In total she counted 320 cells, of which 48 were in mitosis and the remainder were in interphase.
   Explain why most of the cells counted were in interphase.2 marks
3. A student investigates the effect of a chemical on cell division in garlic root tips. She grows one set of roots in water (root tip A) and another set in a solution of the chemical (root tip B), then examines a root tip squash of each with a light microscope. In root tip A she counted 450 cells, of which 63 were in mitosis. In root tip B she counted 380 cells, of which 19 were in mitosis.
   Describe how the student should prepare a root tip squash so that chromosomes can be seen.3 marks