1 Cell Division and Mitosis

2 Cell Division  GROWTH of AN ORGANISM  BUILD and REPAIR OLDER CELLS  For the total number of cells to increase cells must undergo CELL DIVISION!!!  Cell Division—when a “parent” cell produces identical “daughter” cells.  Each second another 25 million cells have just finished dividing to create 2 cells.

3 Cell Division—An Amazing Process!!!  Involves the duplication and sorting of chromosomes into two identical sets  Occurs in 6 continuous stages: interphase, prophase, metaphase, anaphase, telophase, and cytokinesis  IPMATC

4 Life Spans of Different Human Cells LIVER CELLS STOMACH LINING RED BLOOD CELLS SKIN CELLS20 DAYS INTESTINAL CELLS PLATELETS BRAIN CELLS 200 DAYS 2 DAYS 3 DAYS YEARS 10 DAYS 120 DAYS

5 Cell Cycle—sequence of growth and division of a cell

6 Interphase: Gap 1 Stage  Chromosomes not visible  Cell growth/protein production  Cell development

7 What is this DNA stuff?

8 Interphase: S Stage (DNA synthesis)  Chromosomes copied (sister chromatids held together by centromere)

9 Interphase: Gap 2 Stage  Chromosomes coil  Protein synthesis needed for cell division  Centrioles replicate

10 Mitotic Stage  Formation of two identical nuclei  4 stages:  Prophase  Metaphase  Anaphase  Telophase  Cytoplasm divides after mitosis (cytokinesis)

11 Centriole Centriole Chromatin (coiled DNA) (fancy name for chromosome!!!) Chromatin (coiled DNA) (fancy name for chromosome!!!) Nucleus Nucleus How many chromosomes?6 Regular cell before division

12 First Stage of Cell Division-- Interphase  No chromosomes visible yet; just thread-like coils called chromatin  Centrioles present outside the nucleus  Chromatin duplicates (copy of DNA is produced)  Chromatin condenses—forms chromatid  Duplicate is called sister chromatid  Is attached to centromere creating a chromosome

13 Interphase Centriole Centriole Double-stranded chromosome (made of 2 sister chromatids Double-stranded chromosome (made of 2 sister chromatids Double-stranded chromosome Double-stranded chromosome Centromere Centromere How many chromatids?12

14 Photo of cell in interphase

15 Beginning of Mitosis-- Prophase  Centrioles move to opposite poles (ends) of the cell  Mesh-like spindle forms (“bridge” between ends of cells)  Nuclear membrane dissolves

16 Chromosome (chromatids) Chromosome (chromatids) Centriole Centriole Centromere Centromere Aster Aster Spindle fibers Spindle fibers Prophase How many chromosomes? 6-doubled stranded

17 Photo of cell in prophase

18 Metaphase  Chromosomes line up at the “equator” and attach to spindle fibers at the centromere

19 Metaphase How many chromosomes?6 double- stranded

20 Photo of cell in metaphase

21 Anaphase  Centromere splits, allows chromosome to separate into 2 sister chromatids  Chromosomes pulled towards centrioles along spindle fibers.

22 Anapahse Chromosome (chromatids) being pulled away from each other towards opposite poles Chromosome (chromatids) being pulled away from each other towards opposite poles How many chromosomes? 12, but 6 going opposite direction

23 Telophase—End of Mitosis  Chromosomes coil again, begin to resemble chromatin; cannot be seen under microscope  Nuclear membrane forms around chromatin  Nucleolus reappears

24 Photo of cell in anaphase

25 Telophase How many chromosomes? 6 in each new nucleus

26 Photo of cell in telophase

27 Cytokinesis—2 new cells  Cytokinesis—the actual division of the cells  Cell membrane moves inward, pinches the cytoplasm into 2 equal parts  Each part contains a nucleus with IDENTICAL CHROMOSOMES

28 Regular cells after division 2 new identical cells!!! Regular cells after division

29 Phases of mitosis—I (PMAT) C

30 Mitosis: Can you name the stages?

31 Animal vs. Plant Cell Division ANIMAL CELL ANIMAL CELL  Centriole and aster present  Daughter cells separated by cleavage furrow PLANT CELL PLANT CELL  No visible centriole or aster  Daughter cells separated by cell plate

32 Duplicated Chromosome