The cell cycle
Cells do NOT divide continuously but undergo a regular cycle of division separated by periods of rapid growth. this is known as the cell cycle and there are three stages:
1) Interphase. this occupies most of the cell cycle and is sometimes known as the resting phase because no division takes place. it is divided into tree parts:
a) first growth (G1) phase, when proteins from which cell organelles are synthesised are produced.
b) Synthesis (S) phase, when DNA is replicated
c) Second growth (G2) phase, when organelles grow and divide and energy stores are increased
2) Nuclear division. when the nucleus divides wither into two (mitosis) or four (meiosis)
3) Cell division. which follows nuclear division and is the process by which the whole cell divides in two (mitosis) or four (meiosis)
So what are the three stages of the cell cycle??
Interphase - ocupies most of the cell cycle
- no division takes place
- three stages of interphase 1) First growth (G1)
2) Synthesis (S)
3) Second growth (G2)
Nuclear division - nucleus divides
Cell division - the whole cell divides
Typically, a mammalian cell takes about 24 hours to complete a cell cycle, of which 90% is interphase.
Cancer is the result of damage to the genes that regulate mitosis and the cell cycle. this leads to uncontrolled growth of cells. as a consequence, a group of abnormal cells, called a tumour, develops and constantly expands in size.
So how long does a typical mammalian cell cycle take??
And what has mitosis got to do with cancer??