Cell cycle control and tumour formation

Overview

Recall questions on the stages of the cell cycle, the G1 and spindle assembly checkpoints, cyclins and cyclin-dependent kinases, apoptosis of damaged cells, tumours and contact inhibition, benign and malignant tumours, metastasis and angiogenesis.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Name the stages of the cell cycle in order, beginning with G1.

   Model answer

   G1, S phase, G2, mitosis and then cytokinesis.

2. 2

   State what happens in S phase.

   Model answer

   The DNA of every chromosome is replicated, so each chromosome comes to consist of two identical sister chromatids.

3. 3

   What is the purpose of a cell cycle checkpoint?

   Model answer

   It halts the cycle until specific conditions are met, so that a cell that is too small, short of nutrients or carrying damaged DNA does not divide.

4. 4

   State three things assessed at the G1 checkpoint.

   Model answer

   Whether the cell has grown large enough, whether nutrients and growth signals are available, and whether the DNA is undamaged.

5. 5

   What is checked at the spindle assembly checkpoint during metaphase?

   Model answer

   That every chromosome is correctly attached to spindle fibres from both poles, so the chromatids will be separated evenly.

6. 6

   Explain the roles of cyclins and cyclin-dependent kinases in driving the cell cycle.

   Model answer

   Cyclin concentrations rise and fall through the cycle, and a cyclin binds and activates its cyclin-dependent kinase, which then phosphorylates target proteins that push the cell past a checkpoint into the next stage.

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