Answer/Explanation:
The cell cycle consists of interphase and mitosis (M). Within interphase, there are three phases: G1, S, and G2.
G1 phase - the first 'gap' phase.The cell grows in size, and synthesises the necessary mRNA and proteins required to divide. This is also where the key decision as to whether the cell will divide takes place. This is based on whether or not the environmental conditions are favourable for division and whether the cell is receiving the correct signals to divide. This is called the G1/S transition, and is the critical decision making point as to whether the cell cycle will progress.
S phase - the 'synthesis' phase. The cell replicates its DNA in preparation for passing the genetic material onto the daughter cells. Once the cell's DNA is replicated, it enters G2.
G2 phase - the second 'gap' phase. The cell continues to grow in size and prepare for mitosis. There is a DNA damage checkpoint here, where the cell ensures that the DNA has properly replicated. Next, it moves into mitosis (M).
M phase - the mitosis phase. This consists of 4 stages (PMAT) - prophase, metaphase, anaphase, telophase. The cytoplasm divides during cytokinesis
- During prophase the chromosomes condense and pair up. The mitotic spindle forms, and the nuclear membrane disappears.
- During metaphase, the chromosomes line up at the centre of the cell - at the metaphase plate. The mitotic spindles attach to the chromosomes - to each sister chromatid.
- During anaphase, the sister chromatids are pulled apart to opposite poles of the cell
- During telophase, two new nuclei form, surrounding the two new sets of chromosomes. Cytokinesis then occurs, pinching the membrane to create two new cells.
