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Mitosis & Meiosis

Explore the reasons why cells divide instead of growing bigger, likening cells to cities and understanding the phases of the cell cycle - interphase, mitosis, and cytokinesis. Delve into the differences between gametes and body cells, and learn about haploid and diploid cells.

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Mitosis & Meiosis

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  1. Mitosis & Meiosis

  2. Why do cells divide rather than grow bigger? • Have you ever been in a traffic jam in a small town? • Where are major traffic jams found? • As a city’s population grows, more people are moving in an out which causes traffic • Cells are like cities • The bigger they are, the more food, water, and waste that must move in and out to keep the cell alive.

  3. Why do cells divide rather than grow bigger? • To prevent traffic jams, they will divide • Cells divide for 4 major reasons: • 1. Prevent the cell from becoming too big (prevent traffic jam) • 2. To heal injuries • 3. To allow the organism to grow (up) • 4. To reproduce (new individuals)

  4. Before we get started with the cell cycle….Lets talk about chromosomes Chromosome: DNA-containing structure that carries genetic material from one generation to another.

  5. What happens during the cell cycle? • Cell Cycle- Process of cellular reproduction, occurring in the main stages • Interphase (growth) • Mitosis (nuclear division) • Cytokinesis (cytoplasm division)

  6. What occurs during Interphase(the 1st step in cell cycle) • There are 3 stages during interphase: • 1st Grows 2ndDuplicates DNA 46 Chromosomes 92 Chromosomes 3rd Prepares to divide

  7. Clicker Question #1 Which of the following is NOT a reason cells divide? To heal injuries To allow the organism to grow To reproduce To maintain homeostasis

  8. Clicker Question #2 What will happen if the cell continued to grow rather than divide? The organism would get too big Food & wastes would not be able to move in & out as easily The surface area would increase and allow more materials into and out of the cell Nothing would happen

  9. Clicker Question #3 What are the 3 stages of the cell cycle? Prophase, Metaphase, & Anaphase Mitosis, Telophase, & Cytokinesis Interphase, Metaphase, & Prophase Interphase, Mitosis, & Cytokinesis

  10. Clicker Question #4 Which of the following is NOT a stage during interphase? Growth (G1) DNA replicates (S) Prepares to divide (G2) Mitosis (M)

  11. What is Mitosis? Mitosis: 2nd main stage of the cell cycle during which the cell’s replicated DNA divides and 2 genetically identical diploid daughter cells are produced.

  12. What occurs during mitosis? (the 2nd step in cell cycle) • There are 4 stages during mitosis: • 1st Prophase (pro = 1st) • 2nd Metaphase • 3rd Anaphase • 4th Telophase (telo = end)

  13. What occurs during mitosis? (the 2nd step in cell cycle) • There are 4 stages during mitosis: • 1st Prophase (pro = 1st) Nucleus disappears Centrioles separate

  14. What occurs during mitosis? (the 2nd step in cell cycle) • There are 4 stages during mitosis: • 2nd Metaphase Chromosomes line up in the middle

  15. What occurs during mitosis? (the 2nd step in cell cycle) • There are 4 stages during mitosis: • 3rd Anaphase Chromosomes move apart

  16. What occurs during mitosis?(the 2nd step in cell cycle) • There are 4 stages during mitosis: • 4th Telophase (telo = end) Nucleus reappears Cytoplasm starts to separate

  17. What occurs during cytokinesis?(the 3rd step (LAST) in cell cycle) • Cytokinesis: The last stage of the cell cycle, during which the cell’s cytoplasm divides, creating a new cell. Daughter Cells

  18. Clicker Question #5 Mitosis creates: 4 genetically identical cells 2 genetically identical cells 4 genetically different cells 2 genetically different cells

  19. Clicker Question #6 What are the 4 stages of mitosis in order? Interphase, prophase, metaphase, anaphase Interphase, prophase, metaphase, telophase Prophase, metaphase, telophase, cytokinesis Prophase, metaphase, anaphase, telophase

  20. Clicker Question #7 This is the last phase of the cell cycle where the cell’s cytoplasm divides to create 2 daughter cells: Cytokinesis Interphase Telophase Metaphase

  21. Now, lets look at the difference between gametes & body cells.

  22. What is the difference between gametes & body cells? Gametes – A haploid sex cell, formed during meiosis, that can combine with another haploid sex cell and produce a diploid fertilized egg. Sperm & Egg are gametes! How many chromosomes are in human gametes? 23

  23. What is the difference between gametes& body cells? How many chromosomes do we have in each of our body cells (not sex cells)? What are “body cells”? Does more chromosomes an organism has mean that it is more advanced/smarter? Brain cells Eye cells Heart cells Tongue cells Skin cells Muscle cells Blood cells Lung cells Kidney cells Nerve cells Everything EXCEPT GAMETES! No…example: King Crabs have 208 chromosomes in each cell No…example: Turkeys have 82 chromosomes in each cell Humans have 46 in our body cells

  24. Body cells reproduce using mitosis. Start with 1 diploid Notice that they are IDENTICAL! End with 2 diploid

  25. What is the difference between diploid and haploid? Diploid – Having two copies of each chromosomes (2n) Body cells are Diploid If you see Diploid… Fruit flies have 8 Skunks have 50 Humans have 46 You think DOUBLE!

  26. Diploid Video

  27. What is the difference between diploid and haploid? Haploid – Cell with half the number of chromosomes (n) Gametes are Haploid 23 23 23 23 If you see haploid… Humans have 23 (in sex cells) Remember: Humans have 46 (in body cells) Fruit flies have 4(in sex cells) Remember: Fruit Flies have 8 in body cells Skunks have 25(in sex cells) Remember: Skunks have 50 in body cells You think HALF!

  28. Haploid Video

  29. Clicker Question #8 Sperm and eggs are: gametes somatic cells body cells all of the above

  30. Clicker Question #9 How many chromosomes are in human gametes? 36 23 20 15

  31. Clicker Question #10 Which of the following is an example of a haploid cell? brain cell skin cell heart cell sperm cell

  32. Clicker Question #11 Mitosis results in: 2 diploid cells 2 haploid cells 4 diploid cells 4 haploid cells

  33. Gametes are formed using meiosis Starts with 1 diploid Notice that they are NOT IDENTICAL Ends with 4DIFFERENT haploid

  34. What happens during Meiosis? Meiosis: Reduction division process, occurring only in reproductive cells, in which 1 diploid (2n) cells produce 4 haploid (n) cells that are NOT genetically identical. Creates EGGS inside the ovaries of females Creates SPERM inside the testes of males

  35. What happens during Meiosis? There are 2 stages during Meiosis: Meiosis I & Meiosis II Meiosis I is exactly like mitosis EXCEPT that Crossing-over occurs during prophase I

  36. What happens during Meiosis? Crossing-over: Exchange of chromosomal segments between a pair of homologous chromosomes during prophase I of meiosis Meiosis I Meiosis II

  37. Why is crossing-over so important?(cuz it is) • It creates genetic variation! • Even though you look similar to your siblings (if same parents), there will never be another person exactly like you because of crossing-over…your parents could have a million kids, and not one of them will look exactly like you! • (except for identical twins, but even they have some differences) Genetic variation allows some individuals to: * Run faster than you * “Look better” than you * Fix things better than you * Paint better than you * Solve math problems better than you * Sing better than you * Train animals better than you * Farm better than you * Fly airplanes better than you * Dance better than you * Swim better than you * Jump better than you

  38. Crossing-Over Continued… Crossing-over occurs between homologous chromosomes. Homo means ___? The same crossing-over patterns do not occur…they create all different kinds of combinations…often called “recombination”…this makes us genetically unique. SAME Homologous Chromosomes means that they contain the SAME genes, in the SAME order as each other, but the message in the genes may be slightly different between the two. - So your mom’s code could be for blue eyes - And your dad’s code could be for brown Being genetically unique creates genetic diversity! …diversity is GOOOOD! Genetic diversity allows some individuals of the same species to continue as their environment changes…even if others can’t survive.

  39. Hypothetical….lets say you are a duck… And shaking your tail feathers will help you find a mate… cuz that is what the ladyz are look’n for Then this is the duck that will pass on his genes!

  40. Hypothetical…lets say you are a caveman Which of these would be LESS likely to survive? Because all these cave people have genetic diversity, but one lacks an important trait (ability to build tools), he will not survive his environment… butthe others will!

  41. What happens during Meiosis? Next is Meiosis II…. * The division process happens again…BUT Meiosis I The DNA does NOT copy before dividing & No crossing-over Meiosis II Results in 4haploid cells that are NOTidentical

  42. Clicker Question #12 Which of the following cells are formed during meiosis? skin cells liver cells egg cells kidney cells

  43. Clicker Question #13 Which of the following cells are formed during mitosis? skin cells sperm cells egg cells all of the above

  44. Clicker Question #14 Meiosis results in: 2 identical haploid cells 4 identical haploid cells 4 different haploid cells 2 different haploid cells

  45. Clicker Question #15 This allows some individuals of the same species to continue as their environment change even if others can’t survive identical twins cloning genetic variation biodiversity

  46. Clicker Question #16 The exchange of chromosomal segments during meiosis is called: interphase crossing-over transcription exchanging-over

  47. Clicker Question #17 Which of the following allows for genetic diversity? meiosis mitosis homeostasis all of the above

  48. Houston…We have a problem… Non-disjunction: Cell division in which the sister chromatids do NOTseparatecorrectly, resulting in gametes with an abnormal number of chromosomes. This is how Down Syndrome happens…the chromosomes don’t separate correctly, and too many end up in the gamete. People with Down Syndrome have 47 chromosomes instead of ____. These are correct! No problem Notice there are NO chromosomes in these cells! Notice that non-disjunction occurred here too! 46

  49. Click on Link for animation… Meiosis Overview

  50. Page 34 in Comp Book Compare & Contrast Mitosis & Meiosis Mitosis Meiosis * Occurs in body cells Both * Occurs in gametes cells * Divides once * Divides twice (meiosis 1 & II * Creation of new cells * Creates 2 cells * Creates 4 cells * DNA replicates once * Are genetically identical * Are NOT genetically identical * Increases genetic diversity

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