Chapter 12 The Cell Cycle

Chapter 12 The Cell Cycle

Cell Division - the reproduction of cells Cell cycle - the life of a cell from its origin in the division of parent cell until its own division into two Functions of Cell Division Reproduction Growth and development Tissue renewal DNA in the Cell Genome - a cell’s total hereditary endowment of DNA Chromosomes – how DNA is packaged in the nucleus Chromatin – the DNA-protein complex Types of Cells Somatic cells - all body cells except the reproductive cells Gametes – reproductive cells, sperm and egg cells Humans – 46 and 23 chromosomes, respectively Chromosomes (Fig 12.3) Sister chromatids - two identical copies of the chromosome’s DNA molecule duplicated in preparation for cell division Centromere - Specialized region of the chromosome seen as a narrow “waist” when the chromosome is condensed Cell Division Terms (Animation) Mitosis - division of the nucleus Cytokinesis – division of the cytoplasm The cell cycle (Fig 12.4)

M phase - cell cycle phase that includes both mitosis and cytokinesis Interphase - cell cycle phase other than M phase, accounts for about 90% of the cell cycle G1 phase - First growth phase S phase – DNA synthesized to duplicate the chromosomes G2 phase – Second growth phase Subphases of Mitosis (Animations, Fig 12.5 & 12.9) Prophase Prometaphase Metaphase Anaphase Telophase Mitotic spindle - a structure composed of microtubules which is necessary for mitosis (Fig 12.6) Kinetichore - a structure of proteins and specific sections of chromosomal DNA at the centromere Metaphase plate - a plane midway between the two spindle poles Cytokinesis (Fig 12.8) Cleavage furrow - a shallow groove in the cell surface near the old metaphase plate Cell plate - vesicle derived divider between two dividing plant cells Prokaryotic Cell Division Binary fission - division in half by bacteria (Fig 12.10) Cell Cycle Regulation (Fig 12.13 & Fig 12.14) Cell-cycle control system - a cyclically operating set of molecules that both triggers and coordinates key events in the cell cycle Checkpoints - a critical control point where stop and go-ahead signals can regulate the cycle

Cyclins - proteins that get their names from their cyclically fluctuating concentration in the cell Cyclins-dependent kinases (Cdk) - enzymes that drive the cell cycle, they must be paired with a cyclin to be active MPF (M-phase promoting factor) - a Cdk-cyclin pair Cancer Transformation - the process that converts a normal cell to a cancer cell Tumor - a mass of abnormal cells within an otherwise normal tissue Benign tumor - tumor that remains at the original site Malignant tumor - an invasive tumor that will impair the function of one or more organs Metastasis - the spread of cancer cells beyond their original site (Fig 12.17)