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Cell division

Cell division. Objective: describe the processes of mitosis (for growth and repair) and outline the events that occur there. Parts of this powerpoint borrowed from a Powerpoint hosted on www.worldofteaching.com. Cell division in Bacteria.

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Cell division

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  1. Cell division Objective: describe the processes of mitosis (for growth and repair) and outline the events that occur there. Parts of this powerpoint borrowed from a Powerpoint hosted on www.worldofteaching.com

  2. Cell division in Bacteria • Binary Fission=cell division in bacteria and some unicellular eukaryotes -means splitting into two parts -each cell has an exact copy of the circular DNA -EX: e-coli in our intestines divide on average every 30 minutes.

  3. http://diverge.hunter.cuny.edu/~weigang/Images/06-11_binaryfission_1.jpghttp://diverge.hunter.cuny.edu/~weigang/Images/06-11_binaryfission_1.jpg

  4. * The following describes cell reproduction for growth and repair in the body (somatic) cells of eukaryotic organisms, including plants, animals, protozoa, and fungi. • This is Asexual reproduction (one parent cell divides into two identical daughter cells). • a complex process requiring different stages

  5. Cell cycle • =define • -3 stages Interphase (cell growth and DNA replication) Mitosis (nucleus splits) Cytokinesis (cell splits)

  6. Image of the Cell Cycle

  7. Stage 1: Interphase • (means between phases)the stage that takes place before cell division occurs. • - the cell grows to its mature size: doubles in size, copies of organelles are made • Then….. Nucleus Chromatin Nucleolus http://www.sep.alquds.edu/biology/scripts/Biology_english/part_3_4_files/image001.jpg

  8. Interphase cont. • -copies its chromosomes: DNA replicates so there are two identical sets of DNA • -prepares for cell division: grows structures which aid in cell division (centrosome, centrioles, microtubules) • (90% of the entire cycle)

  9. Stage 2: Mitosis • define -4 subphases • Phases of Mitosis • Prophase • Metaphase • Anaphase • Telophase

  10. Prophase: • threadlikechromatin condenses and coils to form a chromosome; • spindle fibers form from the centrosomes, centrioles, and microtubules; • nuclear membrane breaks down into parts.

  11. Metaphase: • chromosomes line up across the center of the cell; • a spindle fiber attaches to the centromere of each chromosome; • centrosomes are now at opposite poles of the cell.

  12. Anaphase: • the centromeres split and the chromatids separate; • each chromatid moves along the spindle fiber to the poles; • the poles move apart and the cell stretches out.

  13. Anaphase cont. • -each pole now has a complete set of chromosomes • {Note: each chromatid is now considered to be full-fledged chromosomes} Spindle Fibers

  14. Telophase: • the chromosomes uncoil and stretch out; • new nuclear mem- branes form (from the old nuclear membrane parts)

  15. Stage 3: Cytokinesis • = the final stage of the cell cycle in which the cell’s cytoplasm divides. • -each daughter cell gets one nucleus, half of the organelles and half of the cytoplasm • Note: -- the new cells formed from mitosis are called daughter cells

  16. * In plants a cell plate forms to separate the halves, and forms new cell membranes, and then a new cell wall forms. Plant cells do not undergo true cytokinesis because they have a cell wall. In Animal cells –the cell membrane pinches in to separate the halves *

  17. Parent cell Chromosomes are copied and double in number Chromosomes line up in center. Chromosomes now split 2 daughter cells identical to original

  18. ** Each daughter cell can then begin the cell cycle back with interphase. Acrostic IpmatC I picked many apples today, Cool! I=interphase , p=prophase, m=metaphase, a= anaphase t=telophase, C= cytokinesis

  19. All daughter cells contain the same genetic information from the original parent cell from which it was copied (asexual reproduction) • Every different type cell in your body contains the same genes, but only some act to make the cells specialize – e.g. into nerve or muscle tissue.

  20. Cell division in multicellular Eukaryotes Most complex organisms originated from a single fertilized egg. Every cell in your body started here, then through cell division the numbers are increased Cell then specialize and change into their various roles

  21. Spindle Fibers Anaphase http://www.enchantedlearning.com/subjects/animals/cell/mitosis/label/labelanswers.GIF

  22. Mitosis Cytokinesis

  23. Chromosome number • Every organism has a different number of chromosomes • Humans have 46 • Fruit flies have 8 • Potatoes have 48 • The number of chromosomes is NOT related to the complexity of the organism

  24. Homologous chromosomes • In Sexual reproduction, each parent contributes half of the DNA to the offspring • So the offspring are not identical to the parent • Homologous chromosomes are the pairs of chromosomes that have instructions for the same traits, • Each parent contributes one from the pair • Humans have 23 pairs (46 total chromosomes)

  25. We will discuss this further when we study genetics and the formation of sex cells (sperm and eggs).

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