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5.2 Mitosis and Cytokinesis KEY CONCEPT Cells divide during mitosis and cytokinesis. 5.2 Mitosis and Cytokinesis I.P.M.A.T.C. Overview of mitosis interphase prophase Please Make Another Two Cells cytokinesis metaphase anaphase telophase 5.2 Mitosis and Cytokinesis Interphase • cell copies DNA Copy DNA! DNA cell nucleus (interphase) 5.2 Mitosis and Cytokinesis Mitosis and cytokinesis produce two genetically identical daughter cells. Parent cell • Interphase prepares the cell to divide. • Synthesis (S) ocurrs during interphase – The DNA is duplicated. • Mitosis and cytokinesis occurs after DNA is copied!! nucleus with DNA centrioles spindle fibers centrosome 5.2 Mitosis and Cytokinesis Synthesis: Copying DNA • A dividing cell duplicates its DNA – creates 2 copies of all DNA – separates the 2 copies to opposite ends of the cell – splits into 2 daughter cells DNA cell nucleus But the DNA starts loosely wound in the nucleus If you tried to divide it like that, it could tangle & break 5.2 Mitosis and Cytokinesis Organizing & packaging DNA DNA cell nucleus DNA has been “wound up” DNA in chromosomes in everyday “working” cell cell nucleus 4 chromosomes in this organism DNA in chromosomes in cell getting ready to divide 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 DNA must be duplicated… chromosomes in cell DNA in chromosomes cell 4 single-stranded chromosomes duplicated chromosomes nucleus duplicated chromosomes 4 double-stranded chromosomes cell nucleus 5.2 Mitosis and Cytokinesis Chromosomes of Human Female 46 chromosomes 23 pairs 5.2 Mitosis and Cytokinesis Chromosomes of Human Male 46 chromosomes 23 pairs 5.2 Mitosis and Cytokinesis Mitosis: Dividing DNA & cells • Step 1: DNA winds into chromosomes – DNA is wound up into chromosomes to keep it organized – Nuclear membrane starts to disappear – Spindle fibers form Wind up! duplicated chromosomes cell nucleus (prophase) 5.2 Mitosis and Cytokinesis Mitosis: Dividing DNA & cells • Stage 2: Chromosomes line up – chromosomes line up in middle – attached to protein spindle fibers that will help them move towards centrioles Spindle fiber Line up! centriole duplicated chromosomes lined up in middle of cell (metaphase) 5.2 Mitosis and Cytokinesis Mitosis: Dividing DNA & cells • Stage 3: Chromosomes separate – chromosomes split, separating pairs – start moving to opposite ends Separate! chromosomes split & move to opposite ends (anaphase) 5.2 Mitosis and Cytokinesis Mitosis: Dividing DNA & cells • Stage 4: Cell starts to divide – cells start to divide – nucleus forms again Divide! (telophase) 5.2 Mitosis and Cytokinesis Cytokinesis: Final separation • Organelles are divided between the two cells • DNA unwinds again – now they can do their every day jobs Bye Bye! (cytokinesis) 5.2 Mitosis and Cytokinesis New “daughter” cells • Get 2 exact copies of original cells – same DNA – “clones” 5.2 Mitosis and Cytokinesis • Cytokinesis differs in animal and plant cells. – In animal cells, the membrane pinches closed. – In plant cells, a cell plate forms. 5.2 Mitosis and Cytokinesis Cell division in Animals 5.2 Mitosis and Cytokinesis Mitosis in whitefish embryo 5.2 Mitosis and Cytokinesis Mitosis in plant cell 5.2 Mitosis and Cytokinesis onion root tip 5.2 Mitosis and Cytokinesis Your turn! What’s happening? 5.2 Mitosis and Cytokinesis Your turn! What’s happening? 5.2 Mitosis and Cytokinesis Your turn! What’s happening? 5.2 Mitosis and Cytokinesis Your turn! What’s happening? 5.2 Mitosis and Cytokinesis Your turn! What’s happening? 5.2 Mitosis and Cytokinesis Your turn! • What happens now? 13.1 Ecologists Study Relationships Any Questions?? Any Questions?? 2009-2010 5.2 Mitosis and Cytokinesis • Mitosis divides the cell’s nucleus in four phases. – During prophase, chromosomes condense and spindle fibers form. 5.2 Mitosis and Cytokinesis • Mitosis divides the cell’s nucleus in four phases. – During metaphase, chromosomes line up in the middle of the cell. 5.2 Mitosis and Cytokinesis • Mitosis divides the cell’s nucleus in four phases. – During anaphase, sister chromatids separate to opposite sides of the cell. 5.2 Mitosis and Cytokinesis • Mitosis divides the cell’s nucleus in four phases. – During telophase, the new nuclei form and chromosomes begin to uncoil.
