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Cell Division - Mitosis So WHY do cells divide? Smaller cells have a larger surface area (cell membrane) to volume (cytoplasm/organelles) ratio and therefore are more efficient in getting things in (nutrients) and out (wastes) of cells. When do cells divide by mitosis? a) during growth b) for repair (regeneration) c) reproduction in single cell organisms During Growth For Repair (Regeneration) Reproduction- for single celled organisms MITOSIS Cell division in body/somatic cells One chromosome after duplication/replication has 2 chromatids! Sister chromatids made during S phase of Interphase It goes from B to C during Anaphase Some vocab Chromosomes- long thread of DNA in nucleus - there are 46 chromosomes in each cell Genes - small section of chromosome/DNA Chromatids- each duplicated strand of chromosome. Centromere- structure that holds the identical pairs of chromosomes (chromatids) together. Cell Cycle •Cell cycle includes interphase & mitosis •Interphase is the longest part of the cell cycle. Interphase G1 = first growth phase ~ 9 hrs S = Synthesis phase ~ 10 hrs G2 = second growth phase ~ 2 hrs Cell cycle memory aid Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis Intelligent People Meet At Three o’Clock Intergalactic People Make A lot of Tiny Cars Ian parties Mainly At Twelve o’Clock Insane People Make A Terrific Casserole Indecisive People Make A Terrifying Child Interesting Peas Make (P)Terodactyl Clocks Insects Poop Mega And Tough Cookies Intelligent Prophets Make Amazing Turkey Casseroles Interphase • Parent Cell – “Resting Phase” • Cell is undergoing normal cell activities (Protein Synthesis, etc..) • Not really ‘at rest’, but not actively dividing! • The Chromosomes are in an extended form and seen as chromatin (DNA+protein) - dense mass. • The nucleus is visible. • Cell size increases • DNA of the chromosome is replicated. Prophase • Chromatin condense so that they are seen to consist of 2 chromatids joined by a centromere. • The centrioles move toward opposite poles of the cell. • Spindle fibers are produced & extend from each centrosomes. • Nuclear membrane starts to disappear • Nucleolus is no longer visible Metaphase • The chromosomes line up at the equatorial plate. • The spindle fibers from each centrioles are attached to the centromeres of the chromosomes. • The nuclear membrane has completely disappeared. Anaphase • • The centromeres splits & the sister chromatids separate as each is pulled to an opposite pole. Single strand chromatid are now called chromosomes Telophase • • • • The chromosomes become longer, thinner, & less distinct New nuclear membrane forms The nucleolus reappears Cytokinesis begins Cytokinesis Cytoplasm divides Cleavage furrow- cytokinesis in animal cells Cell plate forms- cytokinesis in plant cells Two daughter cells are formed with their own nucleus CELL IN INTERPHASE…. Daughter Cells – “Resting Phase” See the chromatin IN SUMMARY -Mitosis is: Nuclear Duplication -Cytokinesis Is Cytoplasmic division Mitosis & Chromosome Terms (ploidy = number) Monoploid or haploid(n)- half the normal condition in animals (ie. Sex cells) Diploid(2n)- normal chromosome condition Tetraploid(4n)- 2times normal condition Humans: n=23 chromosome therefore… 46 chromosome in our body cells & 23 chromosomes in our sex cells If 23 = n; then 46 = 2n; and 92 = 4n Chromosome Interphase: The DNA Replicates & chromosomes are doubled Chromosome Chromatid Chromosome Anaphase: the centromere splits and the 2 chromatids are now 2 chromosomes Chromosome Condition: Interphase: 2n Prophase: 2n Metaphase: 2n Anaphase: 4n Telophase: 4n Whitefish Blastula LAB B-1-3 Drawings: INTERPHASE METAPHASE METAPHASE PROPHASE ANAPHASE DAUGHTER CELLS TELOPHASE ANAPHASE TELOPHASE http://www.iknow.net/CDROMs/cell_cdrom/cellmovies.shtml http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_control.html http://www.cellsalive.com/mitosis.htm Mitosis Tutorial for Students http://www.biology.arizona.edu/Cell_bio/tutorials/cell_cycle/cells3.html http://hrsbstaff.ednet.ns.ca/bfougere/science9assist.htm
