Cell Cylce

The cell cycle is a repeating cycle of cellular growth and division- it occurs during the entire life of an organism, from birth until death.

The cell cycle is typically a four-phase process followed by cytokinesis. An individual cell spends about 90% of its time in the first three phases of the cycle, which collectively is called interphase.

A cell will enter the last phase of the cell cycle called, mitosis, only if it is about to divide.

First growth phase (G1): During this phase the cell grows rapidly and carries on routine functions. For most organisms, this phase occupies the major portion of a cell’s life.

Synthesis phase (S): A cell’s DNA is replicated (copied) during this phase. The DNA transforms from chromatin (one copy; shapeless) to sister chromatids (two copies; “X” shaped).

Second growth phase (G2): In the G2 phase, preparations are made for the nucleus to divide (mitosis). Cell organelles, such as mitochondria, replicate to prepare for two cells. Hollow protein fibers called microtubules are assembled.

The process of one nucleus dividing into two nuclei is known as mitosis.

Each nucleus ends up with an equal amount of chromosomes. During mitosis,

microtubules are used to help move chromosomes to opposite ends of the cell.

The process of the cytoplasm dividing is known as cytokinesis.

Once the cytoplasm has divided, two new cells are formed. They are called daughter cells.

Mitosis and cytokinesis are alike in that they are both crucial parts of the cell cycle AND they are both making two of something.

Mitosis is the process in which two nuclei are formed, and cytokinesis is the splitting of the cytoplasm, which leads to two cells.