Mitosis final

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Mitosis final

  1. 1. Mitosis  Why do cells need to divide?
  2. 2. Recap… Cell theory…  Cells are the basic structural unit of life  Cells are the functional units of life  Cells come from pre-existing cells
  3. 3. Overview Why do cells need to divide?  Repair, growth, development Types of reproduction  Sexual  Genetically different  2 parents  Takes time to develop, better chance of survival  asexual  Genetically identical  One parent  Many offspring very quickly
  4. 4. DNA Blueprint of life, nucleic acid Chromatin  Granular genetic material, spread out in nucleus of non-dividing cells Chromosomes  Condensed genetic material, in dividing cells Sister chromatids  Identical copies of Chromosomes joined by a centromere (“centro-” middle)
  5. 5. Humans 46 chromosomes  46 sister chromatids  One from your mom, one from your dad
  6. 6. Cell Cycle: Life of a Cell
  7. 7. Cell Cycle Interphase  90 % of cell’s life, non dividing  G1 phase  Grows, makes organelles  S phase  DNA Synthesis…DNA replicates  G2 phase  Cell prepares to divide, makes sure it has all important organelles for division M phase  When the cytoplasm and nucleus of the cell divides
  8. 8. Cell Cycle  There are check points in G1, S, and G2  Make sure cell is ready to move onto the next phase (has all necessary organelles, copied DNA, etc.)  Once the cell has past the G1 checkpoint, it will complete the cell cycle  Some cells stay in the G1 phase all their life (muscle cell, brain cells)
  9. 9. Regulators of Cell Cycle Cyclins  Protein that regulates the timing of the cell cycle in eukaryotic cells  Levels of cyclins rise and fall throughout the cell cycle Cyclin-dependent Kinases (cdks)  Enzymes that are activated when they bind with cyclin and they make the cell cycle continue
  10. 10. Regulators Internal  Factors within the cell that control cell cycle  Cyclin and CDKs  Allow cell cycle to proceed only when certain processes have occurred  Replication of chromosomes  Chromosome Attachment to spindle before anaphase External  Factors Outside the cell  Growth factorsmolecules that bind to cell surface that signal cell to divide  Similar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing
  11. 11. M-phase Consists of mitosis and cytokinesis Mitosis  Process by which the nucleus of a cell divides  One parent cell makes two identical daughter cells  This is how organisms repair tissue and grow and develop Cytokinesis-division of the cytoplasm
  12. 12. Depending on cell type…  Mitosis can take a few minutes or a few days  Muscle cells (non-dividing)  Nerve cells (non-dividing)  Skin cells (divide all the time)  Digestive Tract cells (divide all the time)
  13. 13. Life Span of Some HumanCells Cell type Life span Cell division Lining of esophagus 2-3 days Can divide Lining of small intestine 1-2 days Can divide Lining of the large 6 days Can divide intestine Red blood cells Less than 120 days Cannot divide White blood cells 10 hours to decades Many do not divide Smooth muscle Long-lived Can divide Cardiac (heart) muscle Long-lived Cannot divide Skeletal muscle Long-lived Cannot divide Neurons (nerve) cells Long-lived Most do not divide
  14. 14. Prophase 50-60% of time Chromosomes become visible Centrioles develop in cytoplasm near nuclear envelope Centrioles separate and migrate to opposite ends of nuc. Env. Centrosome  Region where Centrioles are found  Organize the “spindle”  Fan like microtubule structure that helps separate chromosomes Plants do NOT have Centrioles
  15. 15. End of prophase  Chromosomes coil together tightly  Nucleolus disappears  Nuclear envelope breaks down
  16. 16. Metaphase  Few minutes  Chromosomes line up in middle (M in metaphase MIDDLE)  Microtubules connect centromere of each chromosome to the 2 poles of spindle
  17. 17. Anaphase  Centromeres joining sister chromatids separate and become individual chromosomes  They are dragged by fibers to opposite poles  Ends when chromosomes stop moving
  18. 18. Telophase  Opposite of prophase  Condensed chromosomes disperse into tangle of material  Nuclear envelope reforms  Spindle breaks apart  Nucleolus becomes visible  At the end 2 identical nuclei in one cell
  19. 19. Cytokinesis  Happens at the same time as Telophase  Division of cytoplasm  Animal Cells  Cell membrane drawn inward until it pinches off and forms 2 id daughter cells  Plant Cells  Cell plate forms between nuclei  Cell Plate develops into separate membrane  Cell wall appears
  20. 20. Regulators of Cell Cycle Cyclins  Protein that regulates the timing of the cell cycle in eukaryotic cells  Levels of cyclins rise and fall throughout the cell cycle Cyclin-dependent Kinases (cdks)  Enzymes that are activated when they bind with cyclin and they make the cell cycle continue
  21. 21. Regulators Internal  Factors within the cell that control cell cycle  Cyclin and CDKs  Allow cell cycle to proceed only when certain processes have occurred  Replication of chromosomes  Chromosome Attachment to spindle before anaphase External  Factors Outside the cell  Growth factorsmolecules that bind to cell surface that signal cell to divide  Similar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing
  22. 22. MEIOSIS
  23. 23.  Gregor Mendel 1822 Austrian monk University of Vienna In charge of the Garden
  24. 24. What Gregor MendelKnew…  Each organism must inherit a single copy of every gene from each of its “parents”  Each of the organisms gametes must contain just one set genes  When gametes are formed, there must be a process that separates the 2 sets of genes so each gamete gets one set
  25. 25. Karyotype  A photograph of a organism’s chromosomes, arranged according to size
  26. 26. Chromosome Number Homologous chromosomes  Chromosome that has a corresponding chromosome from the opposite-sex parent Fruit fly has 8 chromosomes  4 from mom  4 from dad
  27. 27. Diploid Di= two sets Cell that contains both sets of homologus chromosomes  Cell contains  2 complete sets of chromosome  2 complete sets of genes Number of chrms in diploid cell represented by 2N For Drosophilia (fruit fly) 2N=8 Mendel said:  Each adult cell contains two copies of each gene
  28. 28. Haploid  Means “one set”  Refers to cells that contain only one set of chromosomes  Gametes (sex cells)  Represented by N  Drosophilia fruit fly  N=4
  29. 29. How arehaploid (N)gametes madefrom diploid(2N) cells?
  30. 30. Meiosis  Process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
  31. 31. Meiosis  2 distinct stages  Meiosis I  A diploid cell enters here  Meiosis II  At the end of this, the diploid cell that entered meiosis has become 4 haploid cells
  32. 32. Meiosis I  Before meiosis 1, each chromosome is replicate  Then they divide like in mitosis  What happened in mitosis?  PMAT  Tetrad  STRUCTURE MADE WHEN EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME  4 CHROMATIDS IN A TETRAD
  33. 33. Prophase 1  Each chromosome pairs with its homologous chromosome making a tetrad  As they pair up in tetrads, chromosomes exchange portions of their chromatids in the process …. CROSSING OVER
  34. 34. Crossing Over
  35. 35. Metaphase1 Spindle fibers attach to chromosomesAnaphase 1• The spindles pull homologous chromosomes apart to opposite poles/endsTelophase 1• Nuclear membranes form and cell separates into two new cells
  36. 36. Now what do we have? 2 new daughter cells Are they identical to the parents?  No  The parent has 4 chromosomes  Each daughter cell has 4 chromosomes but they are different because of crossing-over Each daughter cell has a set of chromosomes and alleles different from each other and different from the parent diploid cell
  37. 37. Meiosis II  Unlike Mitosis, Neither cell goes through a round of chromosome replication  Each cell’s chromosome has 2 chromatids
  38. 38. Prophase II  Meiosis I resulted in 2 “seemingly” diploid cells  Remember they are genetically different b/c of crossing over in prophase I  We still need to cut this number in half to reach our goal of 4 haploid cells
  39. 39. Metaphase 2  Chromosomes line up in middle Anaphase 2• Sister chromatids separate and move to opposite poles Telophase 2• Meiosis II results in 4 haploid (N) daughter cells• 4 daughter cells contain haploid number of chromosomes, just 2 each
  40. 40. Gamete Formation Male  Haploid gametes produced by meiosis are called sperm Female  Haploid gamete produced by meiosis is called an egg  Cell divisions at the end of meiosis one and two are uneven so one cell gets most of the cytoplasm (the EGG) and the other three are called polar bodies (don’t participate in reproduction)
  41. 41. Mitosis vs. Meiosis Mitosis  Results in the production of two genetically identical DIPLOID cells  Daughter cells have sets of chromosomes identical to each other and to parent cell  MITOSIS allows body to grow and replace other cells  Asexual reproduction Meiosis  Results in four genetically different HAPLOID cells  MEIOSIS is how sexually reproducing organisms make gametes
  42. 42. Genes
  43. 43. Microscope Lab Analysis Mitosis/Meiosis Microscope Lab  Lab notebooks Title “Cell Division Microscope Lab”  MUST sketch each stage and label the power  Label slide name  Stage of mitosis or meiosis  Power of the objective used to observe cell  Need to observe each stage of mitosis and meiosis

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