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MITOSIS & CYTOKINESIS. MITOSIS : The nucleus of a cell is divided into 2 nuclei with the same number & kinds of chromosomes as parent cell. CYTOKINESIS: The division of the cytoplasm into 2 distinct cells.

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mitosis cytokinesis
MITOSIS & CYTOKINESIS
  • MITOSIS: The nucleus of a cell is divided into 2 nuclei with the same number & kinds of chromosomes as parent cell.
  • CYTOKINESIS: The division of the cytoplasm into 2 distinct cells.
  • CHROMOSOMES: Contain the genetic information (DNA) passed on to each generation. They differ in number with ea. Specie.
  • COMPOSITION OF CHROMATIN: Makes up chromosomes.
  • Condenses between cell division, chromosomes become visible.
  • Made up of DNA and proteins. The proteins fold the DNA to fit into the nucleus. DNA is 10,000 X the length of chromo.
  • Don & Ada Olins and Christopher Woodcock discovered that DNA was coiled around histone proteins.
  • Nucleosomes: Bead-like structures of DNA and histones
  • These are tightly compacted so they can separate in mitosis.
chromosomes
CHROMOSOMES
  • CHROMOSOME STRUCTURE
  • Chromotids: Identical parts contained in chromosomes (2)
  • Centromere: Located near the center of chromatids (usually)
  • CELL CYCLE
  • A cell grows, prepares for division, and divides to form 2 new daughter cells.
  • Mitosis (M phase) Active cell division, nucleus into 2 new ones
  • Interphase (G1,G2,& S) Period of non cell division, where other life processes are carried out
  • Cytokinesis Where the cytoplasm and contents divide
  • See fig. 8-10
  • Cells go through the cycle in different rates: muscles vs. skin
interphase
INTERPHASE
  • http://www.micro.magnet.fsu.edu/micro/gallery.html
  • INTERPHASE: The period between cell division
  • G1 (Gap 1): Cellular growth and development takes place
  • S: (DNA Synthesis): DNA replication takes place, synthesizing of proteins
  • G2 (Gap 2): Synthesis of organelles and materials required for cell division. Shortest of the phases.
  • Although this phase seems quiet a lot is going on:
  • synthesizing of mRNA
  • making of proteins
  • DNA is copied
  • ATP is made and utilized
  • specialized cells do most of their work: secretion, movement
prophase6
PROPHASE
  • Longest of the phases taking between 50-60% of total time.
  • Chromosomes become visible because of coiling of chromotin
  • Centrioles separate and go to opposite sides of the cell
  • Centrioles contain tubulin, a microtubule protein
  • Chromosomes attach to fibers (spindles) near the centromere.
  • Spindles help move the chromosomes apart and are developed from the centrioles.
  • Centrioles are composed of microtubules.
  • Plant cells do not contain centrioles.
  • Near the end of the phase coiling becomes tighter, the nucleolus disappears, and the nuclear envelope breaks down.
metaphase
METAPHASE
  • The shortest of the phases lasting only a few minutes.
  • Chromosomes line up across the center (equator) of the cell.
  • Microtubules connect the centromere of each chromosome to the poles of the spindle.
  • Because of their starlike arrangement around the poles of the spindle, these microtubules are called ASTERS.
anaphase
ANAPHASE
  • Begins when the centromeres that joins the sister chromotids split.
  • As they separate the spindle grows longer.
  • The chromosomes move until they have separated into two groups near the poles of the spindles.
  • Anaphase ends when the movement of the chromosomes stops.
  • Force that separates the chromosomes isn’t known.
  • Microtubule cross-bridging
  • Microtubule assembly/disassembly
  • Actinmediated force generation
  • All have been proposed. Problem is that such a small force is needed to move a chromosome that pinpointing the cause is a problem.
telephase cytokinesis
TELEPHASE & CYTOKINESIS
  • Final stage of mitosis
  • Chromosomes uncoil into a tangle of chromatin in the regions where the nuclei of the daughter cells will form.
  • The nuclear envelope reforms around the chromatin.
  • Spindles break apart and nucleolus becomes visible.
  • We now have two nuclei w/ a duplicate set of chromosomes
  • CYTOKINESIS
  • Division of the cytoplasm into two individual cells
  • Takes place in a number of ways:
  • In animal cells the cell membrane moves inward until the cytoplasm in pinched into two parts w/ their own nucleus etc.
  • In plants, a cell plate forms midway between the divided nuclei. It develops into a separate membrane w/ a cell wall.