The Cell Cycle As eukaryotic cells grow and divide, they pass through a cell cycle that consists of 3 stages: • Interphase • Mitosis (cell division) • Cytokinesis (cell division)
The length of time to complete a cell cycle is different for different types of cells: • Embryonic cells divide rapidly • Adult nerve cells may never divide
Stage 1: Interphase • Interphase is the longest stage of the cell cycle • The cell performs its normal functions and, in preparation for cell division, duplicates its genetic material (DNA)
Stage 2: Cell Division - Mitosis Consists of 4 phases:ProphaseMetaphaseAnaphaseTelophase
Mitosis Phase 1:Prophase • DNA compacts into visible form as chromosomes • Each chromosome contains two strands called sister chromatids. • Sister chromatids are held together by a centromere • The nuclear membrane breaks down
Mitosis Phase 2: Metaphase • Chromosomes line up in the middle of the cell.
Mitosis Phase 3: Anaphase • The centromere splits and sister chromatids separate. • They are now called daughter chromosomes. • They move to opposite ends of the cell, pulled by spindle fibres
Mitosis Phase 4: Telophase • Final phase of mitosis. • Chromosomes stretch out and are no longer visible. • A new nuclear membrane forms around each group of daughter chromosomes.
Stage 3: Cell Division - Cytokinesis • Final stage of cell division and cell cycle • The cytoplasm divides and two genetically identical cells are formed. • In a plant cell, a plate develops into a new cell wall • In an animal cell, the cell membrane is pinched off in the centre
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