Chapter 10 Cell Growth & Division

Cell Division There are 2 main reasons cell divides: There are 2 main reasons cell divides: 1. The cell has more trouble trying to move nutrients and wastes across the cell membrane. 2. The larger a cell becomes, the more demands it puts on its DNA. Bottom line – cells need to be replaced Bottom line – cells need to be replaced

Cell Cycle The sequence of growth and division of a cell The sequence of growth and division of a cell An average cycle may be 22 hours An average cycle may be 22 hours Two general periods: Two general periods:  1. growth phase  2. division phase

Interphase (Growth phase)  Most of the cell’s life is spent in interphase  Longest phase – (90% of cell’s growth) Centrioles – help to organize cell division Chromatin – DNA bound protein within the nucleus

Interphase (Growth phase) New DNA is formed during 3 phases: G 1 – 1 st period of growth 1. Increase in size. 2. Makes new proteins and organelles. S 1 – DNA is synthesized or replicated 1. Chromosomes are replicated. 1. Chromosomes are replicated. 2. New DNA molecules are made. 2. New DNA molecules are made. G 2 – final cell growth 1. Shortest phase 2. Prepares cell for mitosis

Terms to know Chromosome – contains genetic information (DNA) passed from one generation to the next Chromosome – contains genetic information (DNA) passed from one generation to the next Spindle – microtubule that helps separate chromosomes Spindle – microtubule that helps separate chromosomes A – centromere: A – centromere: center of chromosome center of chromosome B – chromatids: two B – chromatids: two identical “sister” parts identical “sister” parts of the chromosome of the chromosome

Mitosis (Division phase) 4 phases: (PMAT) 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase

Mitosis Takes place within the nucleus of the cell

4 phases that blend from one to another

Prophase 1 st and longest phase of mitosis 1 st and longest phase of mitosis Chromatin become chromosomes Chromatin become chromosomes Chromatids are joined by centromere Chromatids are joined by centromere Nucleus disappears Nucleus disappears Centrioles migrate to poles Centrioles migrate to poles Spindles are formed Spindles are formed

Metaphase 2 nd phase of mitosis 2 nd phase of mitosis Chromosomes meet in the middle of cell Chromosomes meet in the middle of cell Pulled by spindles Pulled by spindles Each chromosome is attached to top of spindle Each chromosome is attached to top of spindle

Anaphase 3 rd phase of mitosis 3 rd phase of mitosis Centromeres are split apart Centromeres are split apart Chromatids are pulled apart and begin to drift to opposite poles Chromatids are pulled apart and begin to drift to opposite poles

Telophase Final phase of mitosis Final phase of mitosis Begins when chromatids reach poles Begins when chromatids reach poles New nucleus starts to form New nucleus starts to form Chromosomes start to unwind Chromosomes start to unwind Spindles disappear Spindles disappear Cytoplasm begins to divide Cytoplasm begins to divide

Cytokinesis Cytoplasm pinches in half Cytoplasm pinches in half Each daughter cell has an identical set of chromosomes Each daughter cell has an identical set of chromosomes

Plants apical meristem

Rat – epithelial cells

Prophase, Metaphase, Anaphase, or Telophase?