5 2 Mitosis and Cytokinesis KEY CONCEPT Cells

5. 2 Mitosis and Cytokinesis KEY CONCEPT Cells divide during mitosis and cytokinesis. Zebra Book Chpt 9 -2

5. 2 Mitosis and Cytokinesis Objectives for section 5 -2 • Explain the importance of chromosomes condensing at the start of mitosis • Elaborate of the processes of mitosis and cytokinesis to create identical cells.

5. 2 Mitosis and Cytokinesis Chromosomes condense at the start of mitosis. • DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA

5. 2 Mitosis and Cytokinesis • DNA plus proteins is called chromatin. chromatid • One half of a duplicated chromosome is a chromatid. • Sister chromatids are held together at the centromere. • Telomeres protect DNA and do not include genes. telomere centromere telomere Condensed, duplicated chromosome

5. 2 Mitosis and Cytokinesis Mitosis: equal division of nuclear material (chromosomes) -Greek word “mitos” = thread • Genes consist of long threadlike molecules -Creates identical cells -Replaces worn-out cells -Repair -Growth

5. 2 Mitosis and Cytokinesis Spindle apparatus helps chromatids move to opposite sides of dividing cell in mitosis -Made of centrioles, asters & microtubule fibers

5. 2 Mitosis and Cytokinesis Spindle Apparatus Micro tubu les asters Centrioles

5. 2 Mitosis and Cytokinesis Four phases of mitosis -Continuous process followed by cytokinesis 1. Interphase (not part of mitosis) 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase (then cytokinesis)

5. 2 Mitosis and Cytokinesis Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell • Interphase prepares the cell to divide. • During interphase, DNA is duplicated. • “Inter” means between centrioles spindle fibers centrosome nucleus with DNA

5. 2 Mitosis and Cytokinesis • Prophase (Pro” = “before” or “earlier than”). -Chromosomes condense, nuclear envelope breaks down, and spindle fibers form.

5. 2 Mitosis and Cytokinesis • Metaphase (“Meta” = “later than” or “after” – Chromosomes line up in the middle of the cell.

5. 2 Mitosis and Cytokinesis • Anaphase (“Ana” = “up” or “back”) – Sister chromatids separate to opposite sides of the cell.

5. 2 Mitosis and Cytokinesis • Telophase (“Telo” = “end”). – New nuclei form, spindle disassembles, and chromosomes begin to uncoil. -reverse prophase

5. 2 Mitosis and Cytokinesis (division of cytoplasm) differs in animal and plant cells. -Animal cell pinched in half by protein belt (cleavage furrow)

5. 2 Mitosis and Cytokinesis Plants: cell plate forms in middle of cell

5. 2 Mitosis and Cytokinesis Prophase Anaphase Metaphase Telophase Mitosis magnified 2700 times

5. 2 Onion Mitosis and Cytokinesis root mitosis