The ability of all life to replicate itself for future generations originates in the reproduction of cells.

All cells arise from other cells.

Cells have a limited life span.

During cell division, one cell becomes split into 2 cells. The original cell is called the PARENT CELL. The 2 cells resulting from the division are called DAUGHTER CELLS.

CELL CYCLE
– The cell cycle is the entire lifespan of a cell, starting with its production from a previous parent cell and ending with its division into 2 new daughter cells.
– Compared to the rest of the cells’ life, cell division is a brief and distinct stage in the cells’ life.
– The cell cycle is composed of an orderly sequence of phases that are controlled by the DNA of the cells’ nucleus.
– It is composed of an INTERPHASE where the cell is growing larger and replicating its DNA. Then there is nuclear division, called MITOSIS, that has 4 stages; prophase, metaphase, anaphase and telophase. Mitosis ends with the division of the cell into 2 separate daughter cells.

INTERPHASE
– Interphase is not part of cell division. It is a stage when the cell is growing, metabolizing and replicating its DNA.
– All cells spend most of their lives (about 90%) in Interphase. Some cells never leave the stage of interphase.
– Interphase provides enough time for the cell to grow large enough to eventually divide into 2 daughter cells.
– Interphase is divided into 3 stages; G1 phase, S phase and G2 phase.

1. G1 phase or Gap phase
– The cell experiences growth in volume and carries on its normal processes.
– If centrioles (small granules outside the nuclear membrane) are present, they begin to replicate.
– It is the longest phase.

2. S phase
– During Interphase the nucleus exist as a distinct organelle, bound by the nuclear membrane.
– Inside the nucleus are long, thin, unwound strands of chromosomes. These chromosomes influence the activity of the cell.
– This single set of chromosomes replicates itself.
– The genetic information (DNA) is doubled, providing the correct amount of this material for equal distribution during cell division.

3. G2 phase
– In the final stage of Interphase, the nucleus is still well defined.
– Replication of the centrioles is completed.
– The spindle apparatus that helps move the chromosomes during mitosis begins to be assembled.
– The cell chemically prepares for the cell division by replicating organelles and creating the chemicals needed for the actual division process.