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Ch. 10, Cell Growth and Division Ch. 11, Meiosis (sec. 11-4)

Ch. 10, Cell Growth and Division Ch. 11, Meiosis (sec. 11-4). Ch. 10: Cell Growth- why do cells divide instead of continue to grow? Cell Division – Cell Cycle and when a cell divides, Mitosis Regulation of the Cell Cycle- how it’s controlled, what happens when it’s out of control Ch. 11:

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Ch. 10, Cell Growth and Division Ch. 11, Meiosis (sec. 11-4)

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  1. Ch. 10, Cell Growth and DivisionCh. 11, Meiosis(sec. 11-4) • Ch. 10: • Cell Growth- why do cells divide instead of continue to grow? • Cell Division – Cell Cycle and when a cell divides, Mitosis • Regulation of the Cell Cycle- how it’s controlled, what happens when it’s out of control • Ch. 11: • Phases of Meiosis • Comparing Mitosis and Meiosis

  2. Cell Growth I’m out of control! Section 10.1 – Cell Growth Box 3 Understanding the relationship between a cell’s Surface Area and Volume is the key to understanding why cells must divide as they grow. Too Big! Just right TooSmall • How do organisms grow? Do their cells get bigger? Or do they make more cells? • Answer =Make more cells!!! • There is a limit to how big cells can grow! • Getting bigger does 2 things: • Places more demands on DNA • Makes it harder to move molecules across a cell’s membrane Box 1 Box 2

  3. Surface Area toVolume Ratio Surface Area (SA): 1 x 1 x 6 = 6 cm3 (length x width x height x # sides) Box 4 6 sided cube 1 cm 1 cm 1 cm Bigger 6 sided cube Box 5 3 cm 3 cm Volume increases more rapidly than Surface Area and this causes the ratio of SA to V to decrease. 3 cm Decreasing the SA to V ratio causes big problems for the cell. More molecules trying to go through the membrane (SA) and there’s less surface area for everything to move through! Box 6 Bigger is NOT better! Volume (V): 1 x 1 x 1 = 1 cm3 (length x width x height) More surface area! Good! Ratio of SA to V: 6/1 = 6:1 SA: 3 x 3 x 6 = 54 cm3 Less surface area! Bad! V: 3 x 3 x 3 = 27 cm3 Ratio of SA to V: 54/27 = 2:1

  4. Instead of growing bigger, let’s make more cells! And to do this, 1 cell will divide into 2 cells. Box 7 What’s the solution to this traffic problem?

  5. Cell Division I’m too fat daughter daughter Mommy? • When a cell divides, the 2 cells that result are called “daughter” cells • Cell Division = process by which a cell divides into 2 new daughter cells • Before cell division, the cell replicates, or makes copies of all of its DNA • Solves the 2 problems with cell growth: • New daughter cells get one complete set of genetic information- they get their own complete genetic library • No more problems with SA to V ratio because daughter cells has an increased ratio of SA to V because their volume overall is reduced (one cell dividing into two makes both cells smaller) Box 8 Box 9

  6. Cell Division Section 10-2 Genetic information passed from 1 generation to the next is carried by Chromosomes Chromosomes are made up of DNA- the part that carries the cell’s genetic information Box 12 Box 13 Mitosis is considered asexual because cells produced by it are genetically identical to the parent cell. Box 14 • In Eukaryotes (you!), cell division occurs in 2 main stages: • Mitosis = division of the cell’s nucleus • Cytokinesis = division of the cytoplasm Box 11 (Sy-toh-kih-NEE-sis)

  7. Chromosomes chromatid • When a cell isn’t in the process of dividing, chromosomes are not visible because they are spread out within the nucleus. • However, when cell division is beginning, the chromosomes condense into compact, visible structures we can see in a microscope. • Before cell division occurs, each chromosome is copied, or replicated, and the identical copies are called “sister” chromatids(KROH-muh-tids) replication Yo! Sis! LYLAS! Centromere Box 16 Sister chromatid Sister chromatid Box 15

  8. The Cell Cycle Box 19 • Cell Cycle consists of 4 phases: • Mitosis and Cytokinesis = M phase • Growth phase = G1 (“G” = gap) • Chromosome replication = S phase • Preparation for mitosis = G2 Interphase = “in between” period of growth for a cell Box 18 Box 17 • The Cell Cycle is a series of events that cells go through as they grow and divide 1. Cell grows 2. Cell prepares for division 3. Cell divides to form 2 daughter cells (each daughter cell will begin the cell cycle again)

  9. Box 21 G1phase = when cells do most of their growing- cells increase in size and make new proteins and organelles Cell Cycle Phases Box 24 M phase = when cell division occurs Box 22 S phase = when chromosomes are replicated and synthesis of DNA molecules occurs G2phase = when cells make many organelles and molecules needed for cell division Box 23 Box 20 I G1phase I M M phase S phase I G2phase

  10. Mitosis • Interphase then…. • Mitosis has 4 phases: • 1. Prophase • 2. Metaphase • 3. Anaphase • 4. Telophase I then ..PMAT Box 25 Interphase is NOT part of Mitosis!!!!! Remember that!

  11. Mitosis Box 26 Interphase = cell grows and replicates its DNA and centrioles. Interphase Centrioles Nuclear envelope Chromatin

  12. Interphase = cell grows and replicates its DNA and centrioles. Box 27 Prophase= chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down Interphase Spindle forming Prophase Centrioles Centromere Nuclear envelope Chromatin Chromosomes (paired chromatids)

  13. Prophase = chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down. Interphase= cell grows and replicates its DNA and centrioles. Interphase Spindle forming Prophase Centrioles Centromere Centriole Nuclear envelope Chromatin Chromosomes (paired chromatids) Spindle Centriole Metaphase Box 28 Metaphase = chromosomes line up across the center of the cell, each chromosome is connected to a spindlefiber at its centromere

  14. Prophase = chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down. Interphase = cell grows and replicates its DNA and centrioles. Interphase Spindle forming Prophase Centrioles Centromere Centriole Nuclear envelope Chromatin Chromosomes (paired chromatids) Spindle Centriole Individual chromosomes Metaphase Box 29 Anaphase = sister chromatids separate into individual chromosomes andmove apart Metaphase = chromosomes line up across the center of the cell, each chromosome is connected to a spindle fiber at its centromere Anaphase

  15. Prophase = chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down. Box 30 Telophase = chromosomes gather at opposite ends of the cell and lose their distinct shapes- 2 new nuclear envelopes form Interphase = cell grows and replicates its DNA and centrioles. Interphase Spindle forming Prophase Centrioles Centromere Centriole Nuclear envelope Chromatin Chromosomes (paired chromatids) Spindle Centriole Telophase Individual chromosomes Metaphase Nuclear envelope reforming Anaphase = sister chromatids separate into individual chromosomes and are moved apart Anaphase

  16. Interphase = cell grows and replicates its DNA and centrioles. Prophase = chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down. Box 31 Cytokinesis = cytoplasm pinches in ½ , each daughter cell has an identical set of chromosomes Interphase Spindle forming Prophase Centrioles Centromere Centriole Nuclear envelope Chromatin Chromosomes (paired chromatids) Spindle Cytokinesis Centriole Telophase Individual chromosomes Metaphase Nuclear envelope reforming Anaphase = sister chromatids separate into individual chromosomes and are moved apart Telophase = chromosomes gather at opposite ends of the cell and lose their distinct shapes- 2 new nuclear envelopes form Anaphase

  17. Prophase = chromatin condenses into chromosomes, centrioles separate, spindle forms, nuclear envelope breaks down. Interphase = cell grows and replicates its DNA and centrioles. Cytokinesis = cytoplasm pinches in half, each daughter cell has an identical set of duplicate chromosomes Interphase Prophase I…then PMAT Cytokinesis Metaphase Metaphase = chromosomes line up across the center of the cell, and each is connected to a spindle fiber at its centromere Telophase = chromosomes gather at opposite ends of the cell and lose their distinct shapes- 2 new nuclear envelopes form Telophase Anaphase Anaphase = sister chromatids separate into individual chromosomes and are moved apart

  18. Product of Mitosis? 2 identical daughter cells Box 32 Prophase Interphase Metaphase Cytokinesis Anaphase Telophase

  19. Cell Cycle Tree Map Cell Cycleincludes….. Mitosisis divided into… Interphaseis divided into… G1 phase G2 phase S phase Telophase Prophase Metaphase Anaphase And then………Cytokinesis

  20. Draw the cell cycle diagram on pg. Label the parts. List the stages of the cell cycle, describe what happens in each stage (G1, G2, S and M) Title: The Cell Cycle and Mitosis Your Name:ex. by Fred Cooks 1st : The Cell Cycle & Interphase Prophase. Draw a cell in prophase using pg. 246 as a reference. List 3 facts describing events in Prophase. P 2nd : Mitosis - Prophase M 3rd : Mitosis - Metaphase Metaphase. Draw a cell in metaphase, and list 3 facts describing events in this phase. A 4th : Mitosis - Anaphase T 5th : Mitosis - Telophase Anaphaseand Telophase. Draw a cell in anaphase and telophase, and list 3 facts describing events in each phase. 6th : Cytokinesis Include these definitions: Cytokinesis. Draw a cell in cytokinesis and define what happens to the cell. Chromosome Centromere Centriole Spindle Sister chromatids

  21. Regulation of the Cell Cycle Section 10-3 Box 25 • For very obvious reasons, the cell cycle is a tightly, highly controlled process. • Do you know why? • Uncontrolled cell growth is cancer!!!Cancer can be deadly! • Not all cells need to divide all the time, or at all. • There is a time and place for cell division, and controlling the cell cycle is important because it is part of homeostasis- keeping an organism alive and healthy. Box 25 Box 33 Box 25 Box 34

  22. Controls on Cell Division In the lab, scientists can grow cells by placing them in a petri dish, along with nutrients. If you remove cells from the center of the dish, cells bordering the open space begin dividing and filling the empty space. Cells will grow until they form a single layer covering the bottom of the dish, then they stop growing when they come into contact with one another. These experiments show that controls on cell growth and division can be turned onand off. Box 35

  23. What happens in your body? • Similar processes happen in your own body. • What if you get a cut on your finger? A broken bone? • When you’re injured, cells at the edge of the cut or break are stimulated to divide rapidly and produce new cells, starting the process of healing. • When the gap is repaired, the controls for cell division turn off again, and everything returns to normal. Box 27 Box 36

  24. Cell Cycle Regulators • Tim Hunt and Mark Kirschner found a protein that, when injected into non-dividing cells, would cause mitotic spindle fibers to form. • Levels of this protein rose and fell, depending on the phases of the cell cycle – produced when needed for division, not produced when no cell division is occurring. • They called the protein Cyclin (for cycle) • Cyclins = regulate the timing of the Cell Cycle in Eukaryote cells (your cells!) Box 28 Box 37 Box 29 Box 38

  25. Hunt and Kirschner’s Experiment A sample of cytoplasm is removed from a cell in mitosis. Box 30 The reason for this effect is the proteinCyclin, whichtriggers cell divisionin non-dividing cells. The sample is injected into a second cell in G2 of interphase. As a result, the second cell enters mitosis.

  26. Internal and External Regulators Box 31 Box 39 • Internal regulators = regulating proteins that respond to events inside the cell, and control the cell cycle; allow cell cycle to proceed only when certain process have happened inside the cell. • Similar to: You can’t eat your dessert until you clean your plate! • External regulators = regulating proteins that respond to events outside the cell, and control the cell cycle Box 32 Box 40

  27. Uncontrolled Cell Growth Box 42 44.77% chance of a man getting cancer 33.08% chance of a woman getting cancer • Cancer. • Such a scary word, isn’t it? • Most common cancers: • Men: Prostate cancer (33%) Lung (13%) • Women: Breast (32%) Lung (13%) Affects 1 in 6 men Box 41 Box 33 Affects 1 in 13 men Affects 1 in 7 women Affects 1 in 17 women Box 34 Pretty frightening, yes? American Cancer Society 2004 Statistics

  28. Cancer Box 43 Tumors = masses of uncontrollably dividing cells that damage surrounding tissues Box 44 • Cancer cells may Metastasize, or break loose and spread throughout the body. Untreated Breast Cancer Tumor on the eye • Cancer cells do not respond to the signals that regulate growth of most cells. • They divide uncontrollably and form masses of cells called Tumors that can damage the surrounding tissues. Box 35 Box 36

  29. Cancer • Cancer is a disease of the Cell Cycle. • To find a cure for this horrible disease, we must first deeply and completely understand the Cell Cycle, what regulates it, and how it can go wrong, resulting in cancer. • This is a major scientific challenge, but at least we know now where to start searching for a cure- the Cell Cycle. Box 37 Box 45

  30. Stem Cells • When you were first conceived, you started out as a SINGLE cell. One cell. • That one cell then divided over and over, (Mitosis) producing cells that could and would become all the specialized parts of your body. • Fetal Stem Cells= the cells in the earliest stages of fetal (baby) development, they can potentially become any cell type in the body. • Adult Stem Cells = usually found in the bone marrow, can be induced (pushed) to become other cell types like muscle, nerve and liver cells Controversial – Unethical? Box 38 Box 46 Box 47 Box 39 Has the promise to repair many injuries and replace damaged organs (ex. liver)

  31. Meiosis Section 11-4 46 Box 40 Box 48 • Humans have 46 chromosomes in every cell of our bodies except the sex cells or gametes (eggs and sperm)- they have 23 chromosomes • When a baby is conceived, an egg from mom and a sperm from dad, combine into the first cell of the new baby. 23+23 = 46 Box 49 Box 40 Box 50 46 What would happen if the egg and sperm both had 46 chromosomes? Baby would have 92 chromosomes!! Disaster! 92 chromosomes = death, disease

  32. Remembering Meiosis Box 51 • Mitosis is a process that occurs in almost every cell of your body (body cells), except the sex cells, or gametes. • Mitosis = My toe sis, it happens in your toes! • Meiosis is a process of cell division that doesn’t happen in your toes, it only happens in your sex cells, gametes • Meiosis = My OH! Sis (as in uh-oh!) Box 40 Box 52

  33. Meiosis Box 55 Meiosis results in cells with ½ the # of chromosomes, so they can combine in sexual reproduction, which results in an embryo with the normal amount of chromosomes. • To solve this problem, the cells in the gametes (eggs and sperm), undergo Meiosis instead of Mitosis, when they divide. • Why Meiosis? • Most cells in our body are Diploid (“di” = 2) • Diploid = have 2 sets of chromosomes, 2n(one from mom, one from dad) • Sex cells, or gametes, are Haploid • Haploid = have 1 set of chromosomes, 1n Box 53 Box 41 Box 54 Box 42

  34. Chromosome Number Box 56 Homologous chromosomes= 2 sets of similar chromosomes, one from mom, one from dad • An example. • Fruit Flies (Drosophila), have 8 chromosomes total – 4 from dad fruit fly, 4 from mom fruit fly. Box 43 2n = 8 Diploid number? Haploid number? 1n = 4

  35. Phases of Meiosis Homologous = same chromosome, it just comes from different parents (mom or dad) • How are haploid (1n) gamete cells produced from diploid (2n) cells? • By Meiosis (my-OH-sis) • Meiosis = process of reduction cell division where the # of chromosomes per cell is cut in ½ by the separation of homologous chromosomes Box 57 Box 45 Box 58 Box 46 • Meiosis involves 2 distinct divisions, • Meiosis I • Meiosis II • Results of Meiosis? = cells with a haploid (1n) number of chromosomes Box 59

  36. Meiosis I Box 61 Prophase I = Each chromosome pairs up with its matching homologous chromosome forming a tetrad Interphase I = Cells undergo a round of DNA replication, forming duplicate chromosomes Tetrads= in prophase I, chromosomes duplicate and form a structure with 4 chromosomes (tetrad) Box 60 Box 62 4 sister chromatids form a Tetrad 2 sister chromatids Interphase I Prophase I Chromosome duplication

  37. During prophase I of Meiosis, when the tetrads form, a phenomenon called “Crossing Over” can occur. Crossing Over = results in the exchange of genetic information between homologous chromosomes Box 63 You got peanut butter in my chocolate! You got chocolate in my peanut butter! Sorry! Hey hot stuff, wanna dance? Owww! My arm! Who me? I think he likes me! Help!

  38. Meiosis I Anaphase I = Fibers pull the homologous chromosomes towards opposite ends of the cell (“A” for apart) Prophase I = Each chromosome pairs up with its corresponding homologous chromosome to form a tetrad Box 64 Metaphase I = Spindle fibers attach to the chromosomes, then they line up in the middle (“M” for middle) Interphase I = Cells undergo a round of DNA replication, forming duplicate chromosomes Box 65 Interphase I Prophase I Metaphase I Anaphase I

  39. Meiosis I Anaphase I = Fibers pull the homologous chromosomes towards opposite ends of the cell (“A” for apart) Prophase I = Each chromosome pairs up with its corresponding homologous chromosome to form a tetrad Metaphase I = Spindle fibers attach to the chromosomes, then they line up in the middle (“M” for middle) Telophase I and Cytokinesis = Nuclear membranes form, the cell separates into 2 new cells Interphase I = Cells undergo a round of DNA replication, forming duplicate chromosomes Box 66 Interphase I Prophase I Metaphase I Anaphase I Telophase and Cytokinesis

  40. Meiosis II Prophase II = of meiosis I results in 2 haploid daughter cells, each with ½ the # of chromosomes as the original cell Box 67 The 2 new cells now enter a 2nd round of meiotic division No more chromosome duplication prophase II

  41. Meiosis II Metaphase II = chromosomes line up in the middle Box 68 metaphase II prophase II Prophase II = of meiosis I results in 2 haploid daughter cells, each with ½ the # of chromosomes as the original cell

  42. Meiosis II Anaphase II = sister chromatids separate and move to opposite ends of the cell Box 69 Prophase II = of meiosis I results in 2 haploid daughter cells, each with ½ the # of chromosomes as the original cell Metaphase II = chromosomes line up in the middle Telophase II and Cytokinesis = of meiosis II results in 4 haploid (1n) daughter cells Box 70 4 3 metaphase II anaphase II telophase II prophase II 2 1

  43. Flow Chart for Meiosis I P Interphase I M Prophase I A Metaphase I Anaphase I T 92 Telophase I &Cytokinesis 92 92 92 Humans = 2n = 46 46 P Prophase II A M T Telophase II & Cytokinesis Anaphase II Metaphase II 46 23 46 46 4 daughter cells with haploid # (1n) I then …PMAT…..PMAT

  44. Gamete Formation For Sexual Reproduction, where egg and sperm unite to make an embryo Box 72 • Why do we even have Meiosis? • To make gametes (eggs and sperm). • Male gametes = sperm • Female gametes = eggs Box 71 Skip Box 59 Why do we need eggs and sperm? End of Chapter 10 and Chapter 11 Section 11-4

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