Mitosis: Cell Division
Why do cells divide? Growth Repair Replace dead cells
What cells divide often? Skin Stomach lining Red Blood cells Embryo Plant roots Hair Nails
What cells rarely/never divide? Nervous System Liver
Why do we age? Eventually cells stop being replaced “Apoptosis” Cell death “We die because out cells die.” William R. Clark
“C” Terms Chromosomes Chromatid Long threads of genetic material Found in nucleus Chromatid One side of a duplicated chromosome
“C” Terms Centromere NOTE Structures that hold sister chromatids together NOTE 2 sister chromatids = 1 duplicated chromosome
“C” Terms Chromatin DNA tnagled around a histone (a protein) Condensed chromatin = chromosome
Huh? C. Duplicated chromosome A. DNA B. Chromatin histone
“C” Terms Centrioles Small protein bodies In cytoplasm Animal cells only
Cell Division in a Nutshell Before: Chromosome duplicates = 2 sister chromatids During: Sister chromatids separate After: 2 “daughter” cells Genetically identical
Cell Cycle Mitotic phase 10% Interphase 90%
Interphase Made up of three phases: What happens? G1, S, G2 Things necessary to divide
Interphase G1 Phase S Phase G2 Phase More Cell Growth 8-10 hours S Phase DNA replication Chromosome replication 6-8 hours G2 Phase More Cell Growth Centriole replication 4-6 hours
Mitotic Phase Mitosis Cytokinesis Division of nucleus (chromosomes) Occurs after interphase Cytokinesis Division of cytoplasm Creates 2 daughter cells Occurs at the end of mitosis
Mitosis Phases IPPMAT Interphase Prophase Prometaphase Metaphase Anaphase Telophase IPPMAT
Task IPPMAT Draw a diagram of mitosis Label 6 phases & give each a short description IPPMAT
Interphase “Resting Phase” Precedes mitosis Prepares cell for division Cell NOT dividing Precedes mitosis Prepares cell for division How?
Early Prophase Centrioles: Chromosomes now visible Make spindle fibres Move towards opposite plates Chromosomes now visible
Late Prophase Centrioles reach poles Nuclear membrane (envelope) & nucleolus start to disappear
Metaphase Spindle fibres attach to centromeres Duplicate chromosomes line up at equator Guided by spindle fibers
Anaphase Spindle fibers retract Pull sister chromatids apart Towards opposite polls
Telophase Chromatin reappears Nuclear membrane & nucleolus reappear Cytokinesis occurs Result Two daughter cells
What phases do you see? B A C D
Cytokinesis Why would it occur differently in animal and plant cells? Plant cells have a rigid cell wall!
Cytokinesis Animal Cells Cell membrane pinches inward Creates cleavagefurrow Think: Pull a string around a balloon Plant Cells Cell Plate forms between two new nuclei Becomes cell wall
Cytokinesis
Cytokinesis
Plant vs. Animal – Another Difference? Centrioles not present in plant cells What makes spindle fibers in plant cells? Form from cytoskeleton
Concept Map