Chapter 9: Cell Division, Mitosis

I.  cell division occurs in all organisms

          A.  growth and repair and renewal

                    1.  surface-area-to-volume ratio remains functional

                    2.  chromosomes: one condensed strand of DNA, contains genetic

                         information

                    3.  chromatin: tangled mass of thin threads of DNA

                    4.  sister chromatids: duplicated chromosome, with 2 identical parts

                    5.  centromere: constriction where sister chromatids are attached to

                         each other

                    6.  kinetochore: the spot on the centromere where the chromatids

                        attach to spindle fibers during cell division

          B.  duplicated eukaryotic chromosome: daughter cells get equal amounts

               of DNA

                    1.  diploid (2n): 2 chromosomes of each kind

                    2.  haploid (1n): 1 chromosome of each kind, found in sex cells

                    3.  human chromosome number: 46 or 23 pairs

          C.  cytokinesis: division of the cytoplasm

          D.  mitosis: nuclear division of chromosomes, where daughter cells will receive the same number of

               chromosomes as the parent cell had

II.  Eukaryotic cell cycle: cells grow and divide

          A.  stages

                    1.  interphase: used to be called resting stage, growth, DNA

                        duplication

                              a.  G₁ stage: organelles begin to double

                              b.  S stage: replication of DNA

                              c.  G₂ stage: synthesis of proteins

                    2.  M stage: mitosis

                              a.  prophase:

                                        1) chromatin condenses

                                        2) nucelolus disappears

                                        3) nuclear membrane disappears

                                        4) spindle fibers appear, made of microtubules

                              b.  metaphase

                                        1) sister chromatids line up at equatorial plate

                                        2) kinetochores attach to spindle fibers

                              c.  anaphase

                                        1) centromeres divide spindle lengthens

                                        2) diploid set of daughter chromosomes move toward

                                            each pole

                                        3) cytokinesis begins

                              d.  telophase

                                        1) chromosomes begin to uncoil

                                        2) nucleolus reappears

                                        3) nuclear membrane reforms

                                        4) spindle fibers disappear

                                        5) daughter nuclei are diploid

                                        6) cytokinesis is nearing completion

                              e.  cytokinesis: cytoplasm cleavage

                                        1) animal cells: cell furrow, indentation of cell

                                            membrane

                                        2) plant cells: cell plate forms from Golgi apparatus

          B.  control of cell cycle: enzymes

                    1.  kinase: removes P from ATP, activate cyclin

                    2.  cyclin: protein that accumulates in the cell

                    3.  kinase-cyclin: start the process of cell division at the beginning

                         of S and M stages

III.  Eukaryotic cells: divide by mitosis

          A.  animal cells

                    1.  centrioles: : centrosome contains centrioles

                    2.  aster: starlike, short microtubules radiate out from pair of

                         centrioles

                    3.  cell furrow, indentation of cell membrane

          B.  plant cells

                    1.  spindle forms without centrioles or asters

                    2.  cell plate forms from Golgi apparatus

IV.  prokaryotes

          A.  nucleoid: circular loop of DNA

          B.  asexual division: divide in half by binary fission