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Honors Biology 2011-12 Biology is the only subject in which multiplication is the same thing as division…

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Presentation on theme: "Honors Biology 2011-12 Biology is the only subject in which multiplication is the same thing as division…"— Presentation transcript:


2 Honors Biology 2011-12 Biology is the only subject in which multiplication is the same thing as division…

3 Honors Biology 2011-12 The Cell Cycle: Cell Growth, Cell Division

4 Honors Biology Where it all began… You started as a cell smaller than a period at the end of a sentence…

5 Honors Biology How did you get from there to here? And now look at you…

6 Honors Biology Getting from there to here…  Cell division  reproduction of cells  continuity of life  reproduction  unicellular organisms  growth  repair & renew  Cell cycle  life of a cell from origin to division into 2 new daughter cells amoeba

7 Honors Biology Getting the right stuff  What is passed on to daughter cells?  exact copy of genetic material = DNA  mitosis  division of organelles & cytoplasm  cytokinesis chromosomes (stained orange) in kangaroo rat epithelial cell  notice cytoskeleton fibers

8 Honors Biology Copying DNA  Matching bases allows DNA to be easily copied

9 Honors Biology Copying DNA  Dividing cell duplicates DNA  separates each copy to opposite ends of cell  splits into 2 daughter cells  human cell duplicates ~3 meters DNA  each daughter cell gets complete identical copy  error rate = ~1 per 100 million bases  3 billion base pairs mammalian genome  ~30 errors per cell cycle mutations

10 Honors Biology DNA replication  Strands “unzip” at the weak bonds between bases by enzyme HELICASE

11 Honors Biology DNA Polymerase Copying DNA  Build daughter DNA strand  use original parent strand as “template”  add new matching bases  synthesis enzyme = DNA polymerase

12 Honors Biology Copied & Paired Up Chromosomes centromere

13 Honors Biology A bit about DNA  DNA is organized in chromosomes  double helix DNA molecule  associated proteins = histone proteins  DNA-protein complex = chromatin  organized into long thin fiber DNA histones chromatin duplicated chromosome

14 Honors Biology human chromosomes

15 Honors Biology Copying DNA with care…  After DNA duplication, chromatin condenses  coiling & folding to make a smaller package  from DNA molecule to chromatin to highly condensed mitotic chromosome DNA chromatin mitotic chromosome

16 Honors Biology Mitotic Chromosome  Duplicated chromosome  2 sister chromatids  narrow at centromeres  contain identical copies of original DNA

17 Honors Biology Cell cycle  Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G 1, S, G 2, M G1G0G1G0 epithelial cells, blood cells, stem cells brain / nerve cells muscle cells liver cells

18 Honors Biology Interphase  90% of cell life cycle  cell doing its “everyday job”  produce RNA, synthesize proteins/enzymes  prepares for duplication if triggered  Characteristics  nucleus well-defined  DNA loosely packed in long chromatin fibers

19 Honors Biology Interphase  Divided into 3 phases:  G 1 = 1 st Gap  cell doing its “everyday job”  cell grows  S = DNA Synthesis  copies chromosomes  G 2 = 2 nd Gap  prepares for division  cell grows  produces organelles, proteins, membranes  PROOFREADING

20 Honors Biology Mitosis  Dividing cell’s DNA between 2 daughter nuclei  4 phases  prophase  metaphase  anaphase  telophase

21 Honors Biology Prophase  Chromatin condenses  visible chromosomes  Centrioles move to opposite poles of cell  Nucleolus disappears  Nuclear membrane breaks down

22 Honors Biology Metaphase  Chromosomes align along middle of cell  metaphase plate  meta = middle  spindle fibers coordinate movement  helps to ensure chromosomes separate properly  so each new nucleus receives only 1 copy of each chromosome

23 Honors Biology Anaphase  Sister chromatids separate  move to opposite poles  In anaphase, chromatids separate to become individual chromosomes 2 chromosomes 1 chromosome 2 chromatids

24 Honors Biology Telophase  Chromosomes arrive at opposite poles  nuclear membranes form  nucleoli form  chromosomes unravel  no longer visible under light microscope  Spindle fibers disperse  Cytokinesis begins  cell division

25 Honors Biology Cytokinesis  Animals  constriction belt of actin microfilaments around equator of cell  cleavage furrow forms  splits cell in two  like tightening a draw string

26 Honors Biology Mitosis in whitefish blastula

27 Honors Biology Cytokinesis in Plants  Plants  cell plate forms  vesicles line up at equator  derived from Golgi  vesicles fuse to form 2 cell membranes  new cell wall laid down between membranes  new cell wall fuses with existing cell wall

28 Honors Biology onion root tip

29 Honors Biology Origin of replication chromosome: double-stranded DNA replication of DNA elongation of cell cell pinches in two ring of proteins Evolution of mitosis  Mitosis in eukaryotes likely evolved from binary fission in bacteria  single circular chromosome  no membrane- bound organelles

30 Honors Biology 2011-12 Any Questions??

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