cell cycle

Question 1

What is the cell cycle?

Answer 1

The sequence of events occurring throughout a typical cell’s life.

Duplicating genomes and then dividing them into daughter cells

Cells enter cell cycle with certain number of chromosomes

Question 2

Describe interphase. Is the structure of chromatin different during interphase?

Answer 2

cells exit mitosis, duplicate genome, divide the genome during mitosis into daughter cells.

1. G1 phase – newley generated daughter cell grows in size and prepares for DNA duplication in the next phase.
2. S phase – cells duplicate their nuclear DNA (DNA SYNTHESS) which remains as chromatin and duplicate the centrosomes (MTOC, forms the mitotic spindles)
3. G2 phase – cells continue to grow and multiply organelles and proteins that are required for mitosis and replenishes their energy stores
4. Mitosis

The structure of chromatin during interphase is different from the structure during mitosis

Question 3

Cell cycle checkpoints

Answer 3

1. G1 checkpoint - Evaluation of a cells external factors (e.g cell’s size, energy, DNA quality). If inadequate then it won’t progress to S phase of interphase.
2. G2 second checkpoint. The cell ensures that all DNA has been replicated and isn’t damaged before entering mitosis. If any are damaged and no repair can be done then cell may undergo apoptosis (programmed cell death)
3. M checkpoint (spindle checkpoint) ensures that all sister chromatids are correctly attached to the spindle microtubules at the metaphase plate before cell enters anaphase.