Cell Cycle

Question 1

Name the 5 phases in the cell cycle

Answer 1

M phase (includes mitosis (prophase, prometaphase, metaphase, anaphase, telophase) an cytokenisis (cell division)

G0 phase - cells are inactive and repair here,

G1 phase - growth phase where cell primes itself for DNa synthesis

S phase - Synthesis phase where DNA synthesis is performed priming for Mitosis.

G2 phase - growth phase prior to Mitosis.

Question 2

How is the cell cycle regulated

Answer 2

Cyclins and cyclin dependent kinsaes. bind together to form complexes that phosphorylate different proteins inorder to progress in cell cycle.

Tumour suppressor genes such as p53 or Rb are involved in restricting cell progression from G1–>S if there is DNA damage. These are damaged in syndromes such as Li Fraumeni syndrome.

Question 3

Cell types: Permanent

Answer 3

Permanent - generated from stem cells and remain in G0, do not undergo division after production –> Neurones, Cardiac and skeletal muscle, RBCs.

Question 4

Cell types: Stable (Quiescent)

Answer 4

Cells that enter G1 if stimulated by damage or environmental factors.

Examples are hepatocytes and lymphocytes.

Question 5

Cell types: Labile

Answer 5

Never enter G0 and are constantly renewing and reproducing. These cells are affected by chemotherapy.

Examples: Bone Marrow, Gut epithelium, Skin, Hair follicles, Germ cells.