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Chapter 2 Cellular Reproduction

Chapter 2 Cellular Reproduction. Chapter Outline. Cells and Chromosomes Mitosis Meiosis Life Cycles of Some Model Genetic Organisms. In both prokaryotic and eukaryotic cells, the genetic material is organized into chromosomes. Cells and Chromosomes. Eukaryotic: 23, non-circular, linear.

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Chapter 2 Cellular Reproduction

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  1. © John Wiley & Sons, Inc. Chapter 2Cellular Reproduction

  2. © John Wiley & Sons, Inc. Chapter Outline • Cells and Chromosomes • Mitosis • Meiosis • Life Cycles of Some Model Genetic Organisms

  3. In both prokaryotic and eukaryotic cells, the genetic material is organized into chromosomes. © John Wiley & Sons, Inc. Cells and Chromosomes Eukaryotic: 23, non-circular, linear Prokaryotic: 1, circular Viruses: 1, DNA circular; 1, RNA linear

  4. © John Wiley & Sons, Inc. The Cellular Environment • Cytoplasm / cytosol / Nucleus/ …the inside of a cell….. Plasma membrane….the outside of the cell… • Water ( 70-80 %) • Hydrophilic and Hydrophobic Molecules; Amphiphatic • Carbohydrates (Glucose and Glycogen) • Lipids (Cholesterol, phospholipids and fatty acids)

  5. The Cellular Environment Proteins (amino acids to polypeptide), including enzymes Ribonucleoproteins, including RNAse as an enzyme Membrane—made of lipids and proteins Cell Wall: cellulose [murein-(sugars and amino acid)-in bacteria) © John Wiley & Sons, Inc.

  6. Animal and Plant Cells Organelles: © John Wiley & Sons, Inc.

  7. © John Wiley & Sons, Inc. Animal and Plant Cells No Organelles:

  8. Animal and Plant Cells © John Wiley & Sons, Inc.

  9. © John Wiley & Sons, Inc. Chromosomes • Double-stranded DNA with associated proteins and sometimes RNA • Prokaryotic cells contain one circular chromosome plus smaller plasmids ( ?) • Most eukaryotic cells contain several large linear chromosomes plus a circular mitochondrial DNA

  10. © John Wiley & Sons, Inc. Vocabulary for Chromosomes • Diploid: cells with 2 copies of each chromosomes • Haploid: cells with one copy of each chromosomes • Somatic cells: any cells of an organism, diploid and go under mitosis. • Germ line: reproductive cells that give rise to gametes • Gametes: specialized cells (sperm and ova) • Centromere: point of interaction of each chromosomes; region of chromosomes required for its movement.

  11. © John Wiley & Sons, Inc. Cell Division in Prokaryotes:Fission • A mother cell divides to produce two daughter cells. • The mother cell’s chromosome is duplicated prior to fission. • Each daughter cell receives one copy of the chromosome and more or less the rest of the content. • Clone—a population of genetically identical cells. • Colony—a visible mass of cells (1 to 250 cells).

  12. Division time? http://mitosissection2.tumblr.com/

  13. © John Wiley & Sons, Inc. Cell Division in Eukaryotes:Inter (I) Phase and Mitosis (M) Phase Go 30 min to

  14. © John Wiley & Sons, Inc. • Cells, the basic units of all living things, are enclosed by membranes. • Chromosomes, the cellular structures that carry the genes, are composed of DNA and protein. • In eukaryotes, chromosomes are contained within a membrane-bounded nucleus; in prokaryotes they are not. • Eukaryotic cells possess complex systems of internal membranes as well as membranous organelles such as mitochondria, chloroplasts, and the endoplasmic reticulum.

  15. © John Wiley & Sons, Inc. • Haploid eukaryotic cells possess one copy of each chromosome; diploid cells possess two copies. • Prokaryotic cells divide by fission (binary) • Eukaryotic cells divide by mitosis and meiosis. • Eukaryotic chromosomes duplicate when a cell’s DNA is synthesized; this event is characteristic of the S phase of the cell cycle.

  16. When eukaryotic cells divide, they distribute their genetic material equally and exactly to their offspring. © John Wiley & Sons, Inc. Mitosis Inter-phase: Chromatin---Heterochromatin ---Eurochromatin M-phase: Chromosomes

  17. © John Wiley & Sons, Inc. Mitosis in Animal Cells mechanical force?

  18. © John Wiley & Sons, Inc. Microtubules, Centrosomes and Centrioles.

  19. Centrosome duplicates (S phase) Centrosomesmove to opposite sides of nucleus during prophase. Mitotic spindle assembles (microtubules=MT) Microtubule organizing centers (MTOCs)

  20. SpindleMTs make contact with chromosomes ---centromere (sequence repeated DNA sequence=heterochromatin =CEN sequences) ---kinetochore (protein-like containing structure)

  21. © John Wiley & Sons, Inc. Cytokinesis inAnimal and Plant Cells Cleavage furrow associated with the contractile ring (Actin and Myosin)

  22. © John Wiley & Sons, Inc. • As a cell enters mitosis, its duplicated chromosomes condense into rod-shaped bodies (prophase). • As mitosis progresses, the chromosomes migrate to the equatorial plane of the cell (metaphase). • Later in mitosis, the centromere that holds the sister chromatids of a duplicated chromosome together splits, and the sisters chromatids separate (or disjoin) from each other (anaphase)

  23. © John Wiley & Sons, Inc. • As mitosis comes to an end, the chromosomes decondense and a nuclear membrane reforms around them (telophase). • Each daughter cell produced by mitosis and cytokinesis has the same set of chromosomes; thus, daughter cells are genetically identical.

  24. Sexual reproduction involves a mechanism that reduces the number of chromosomes by half. © John Wiley & Sons, Inc. Meiosis

  25. © John Wiley & Sons, Inc. Homologues Xx or Xy

  26. © John Wiley & Sons, Inc. Comparison ofMitosis and Meiosis Non-reduction Reduction

  27. © John Wiley & Sons, Inc. Prophase I: Leptonema • Chromosomes condense • Each chromosome has two sister chromatids

  28. © John Wiley & Sons, Inc. Prophase I: Zygonema • Synapsis (pairing) of homologous chromosomes • Synaptonemal complex

  29. © John Wiley & Sons, Inc. The Synaptonemal Complex Function ? Structural...

  30. © John Wiley & Sons, Inc. Prophase I: Pachynema • Chromosomes condense further • Bivalent of chromosomes • Tetrad of chromatids • Crossing over occurs • (exchange material)

  31. © John Wiley & Sons, Inc. Prophase I: Diplonema • Paired chromosomes separate slightly but are in contact as chiasmata

  32. © John Wiley & Sons, Inc. Chiasmata

  33. © John Wiley & Sons, Inc. Prophase I: Diakinesis • Nuclear envelope fragments • Spindle fibers (MT) attach to kinetochores • Chromosomes move to central plane in pairs

  34. © John Wiley & Sons, Inc. Metaphase I • Paired chromosomes are oriented toward opposite poles • Terminalization: chiasmata move toward telomeres • Why?

  35. © John Wiley & Sons, Inc. Anaphase I • Chromosome disjunction (separation of paired chromosomes) • Separated homologues move toward opposite poles

  36. © John Wiley & Sons, Inc. Telophase I • Chromosomes reach the poles; nuclei forms • Spindle apparatus is disassembled • Daughter cells separated by membranes • Chromosomes decondense • Each chromosome still has two sister chromatids

  37. © John Wiley & Sons, Inc. Prophase II • Chromosomes condense • Chromosomes attach to a new spindle apparatus • Sister chromatids are attached to spindle fibers from opposite poles

  38. © John Wiley & Sons, Inc. Metaphase II • Chromosomes align at equatorial plane

  39. © John Wiley & Sons, Inc. Anaphase II • Centromeres split • Chromatid disjunction—sister chromatids move toward opposite poles

  40. © John Wiley & Sons, Inc. Telophase II • Separated chromatids gather at poles; daughter nuclei form • Each chromatid is now called a chromosome • Each daughter nucleus contains a haploid set of chromosomes

  41. © John Wiley & Sons, Inc. Cytokinesis

  42. © John Wiley & Sons, Inc. Daughter cells are NOT genetically identical • Maternal and paternal homologues synapse, then disjoin independently. • Homologous chromosomes exchange material by crossing over

  43. © John Wiley & Sons, Inc. • Diploid eukaryotic cells form haploid cells by meiosis, a process involving one round of chromosome duplication followed by two cell divisions (meiosis I and meiosis II). • During meiosis I, homologous chromosomes pair (synapse), exchange material (cross over), and separate (disjoin) from each other. • During meiosis II, chromatids disjoin from each other.

  44. © John Wiley & Sons, Inc. Human 23 3,200 20 to 25,000

  45. © John Wiley & Sons, Inc. Life Cycle ofSaccharomyces cerevisiae (yeast).

  46. © John Wiley & Sons, Inc. Arabidopsis thaliana, plant

  47. © John Wiley & Sons, Inc.

  48. © John Wiley & Sons, Inc.

  49. © John Wiley & Sons, Inc. Spermatogenesis and Oogenesis in Mammals

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