4.1 Cell Division and Genetic Material
The cell theory:
• all living things are composed of one or more cells
• cells are the smallest units of living organisms
• new cells come from pre-existing cells by cell division
Since all new cells are the product of existing cells, it follows that traits (DNA –deoxyribonucleic) must be passed from one cell, the parent cell, to new cells, the daughter cells.
The Cell Cycle
All somatic cells* go through the cell cycles to make more cells. In multicellular organisms, there are three functions of cell division:
• growth of the organism
• repair of tissues and organs that have been damaged
• maintenance to replace dying or dead cells
Stages of the Cell Cycle
Three main stages of the cell cycle:
• Interphase is the stage of growth and intense cell activity
• Mitosis is the stage of separation of a cell and replicated DNA.
• Cytokinesis is the stage where the division of the cytoplasm occurs to complete the creation of two new daughter cells.
Cell cycle check points – specific points in the cell cycle, monitor growth to ensure the cycle continues when it should. Regulation of the cell cycle occurs through a complex network of signals in the cell. When something interferes with these signals, it results in uncontrolled growth, e.g.: cancer is the result of uncontrolled, rapid cell division which results in a mass of cells called a tumor.
Interphase: the cell grows, develops into a mature, functioning cell, copies its DNA and prepares for division. The three phases of interphase:
o G1 or Growth 1 : rapid growth and cell activity
o S or synthesis: the cellular DNA is copied or replicated and the DNA exists are uncondensed fibres known as chromatin
o G2 or Growth 2: cell synthesis more molecules prior to mitosis and cell division
Mitosis: the cell’s copied genetic material separates and the cell prepares to split...