Continuity of cells

The cell cycle

Actively dividing eukaryotic cells pass through a series of stages known collectively as the cell cycle:

• Interphase - two growth or gap phases (G1 and G2) separated by a synthesis (S) phase
• Mitosis - a nuclear division during which the chromosomal material is partitioned into daughter nuclei
• Cytokinesis - the cell divides into two daughter cells

Interphase

An intense period of metabolic activity as the cell synthesises new components such as organelles and membranes, new proteins and DNA.

• G1 phase - synthesis of macromolecules occurs and volume of cytoplasm and number of organelles increase rapidly
• S phase - DNA duplicated and amount of chromatin doubled. Histones form
• G2 phase - spindle proteins (tubulin) synthesised

Mitosis 

Prophase

• chromatin condenses to form chromosomes
• in animal cells - centrioles move to opposite poles
• spindle begins to form
• as chromosomes continue to condense, they…