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Cell Division

Cell Division. BIO 1113/1114 Oklahoma City Community College. Dennis Anderson. G. A. G. A. T. A. T. Two “handrails” made of sugar and phosphate. G. C. A. Genetic information in the molecule is contained in the sequence of “bases” along one strand of the double helix. In this

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Cell Division

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  1. Cell Division BIO 1113/1114 Oklahoma City Community College Dennis Anderson

  2. G A G A T A T Two “handrails” made of sugar and phosphate. G C A Genetic information in the molecule is contained in the sequence of “bases” along one strand of the double helix. In this example, the order of a few of these bases is CTGA. C C G T T A G G C A A G C A T C G A T

  3. 1.Original DNAmolecule unwinds. 2.New DNA strandsare synthesizedfrom the twooriginal strands.

  4. Figure 9.6aChromosomes and DNA Replication (a)DNA is packaged in units called chromosomes DNA wraps aroundprotein to makechromatin. Chromatin folds up to make chromosomes. G C A T cell duplicated chromosome DNA chromatin

  5. (b)DNAreplicationat two levels DN A replication . . . . . . has this effect at the chromosomal level. unduplicated chromosome (not actual shape) duplicated chromosome sister chromatids

  6. Doubled Chromosome Chromatid Chromatid Single Chromosomes

  7. cell nucleus 1.ReplicationDNA is duplicated. MitosisThe two quantities of DNAare moved to opposite sidesof the parent cell. 3.CytokinesisThe parent cell splitsinto two daughter cells.

  8. Karyotype of Human Chromosomes The two chromosomes above each number are a homologous pair (they are the same in size and function). A human male has onepair of non-homologous chromosomes, X and Y (females have XX).

  9. Cell Cycle • Produces new cells by division • Interphase • Stage when cell is not dividing • DNA duplicates • Mitosis • Series of stages in division of nuclear material • Each daughter cell gets a complete set of chromosomes

  10. Step 1 Mitosis and cytokinesis pair of centrosomes nucleus replicated, uncondensed DNA End of interphase DNA has already duplicated back in S phase. Centrosome has doubled.

  11. Step 2 Mitosis and cytokinesis chromosomes (each a pair of sister chromatids joined together) pair of centrosomes nucleus replicated, uncondensed DNA spindle fibers (microtubules) End of interphase Prophase mitosis begins Chromosomes take shape; the two centrosomes begin to move toward the cellular poles, sprouting microtubules as they go. DNA has already duplicated back in S phase. Centrosome has doubled.

  12. Step 3 Mitosis and cytokinesis chromosomes (each a pair of sister chromatids joined together) mitotic spindle pair of centrosomes nucleus metaphase plate replicated, uncondensed DNA spindle fibers (microtubules) End of interphase Prophase mitosis begins Metaphase attachment and alignment Chromosomes take shape; the two centrosomes begin to move toward the cellular poles, sprouting microtubules as they go. DNA has already duplicated back in S phase. Centrosome has doubled. Microtubules attach to sister chromatids and align them at the metaphase plate.

  13. Step 2 separating chromatids spindle fibers shortening Anaphase separation Sister chromatids are moved to opposite poles in the cell, each chromatid now becoming a full-fledged chromosome.

  14. Step 3 separating chromatids cleavage furrow spindle fibers shortening Telophase and Cytokinesis exit from mitosis Anaphase separation Chromosomes decondense; nuclear envelopes form around the two separate complements of chromosomes. Cleavage furrow begins to form. Sister chromatids are moved to opposite poles in the cell, each chromatid now becoming a full-fledged chromosome.

  15. Step 4 separating chromatids cleavage furrow spindle fibers shortening Telophase and Cytokinesis exit from mitosis Anaphase separation Completion of cytokinesis one cell becomes two Chromosomes decondense; nuclear envelopes form around the two separate complements of chromosomes. Cleavage furrow begins to form. The cell membrane pinches together com- pletely; membranes on either side fuse together creating two cells. Sister chromatids are moved to opposite poles in the cell, each chromatid now becoming a full-fledged chromosome.

  16. Step 5 separating chromatids cleavage furrow spindle fibers shortening Telophase and Cytokinesis exit from mitosis Beginning of interphase Anaphase separation Completion of cytokinesis one cell becomes two These two cells now enter the G1 phase of interphase. Chromosomes decondense; nuclear envelopes form around the two separate complements of chromosomes. Cleavage furrow begins to form. The cell membrane pinches together com- pletely; membranes on either side fuse together creating two cells. Sister chromatids are moved to opposite poles in the cell, each chromatid now becoming a full-fledged chromosome.

  17. 46 46 Mitosis Maintains A Constant Chromosome Number 46

  18. Mitosis Is Used For Growth

  19. Mitosis Replaces Cells That Wear Out.

  20. One Million RBCs per Minute Are Produced By Mitosis

  21. Apoptosis • Process of destroying cells in the body • Enzymes cut cell into many small fragments • Kills damaged skin cells from a sunburn • Prevents skin cancer

  22. Cancer • Uncontrolled cell division • Mitosis too frequent • Apoptosis too slow

  23. The End

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