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Chapter 2 Cellular Reproduction and Model Genetic Organisms

Chapter 2 Cellular Reproduction and Model Genetic Organisms. José A. Cardé-Serrano, PhD Biol 223 – Genética Universidad Adventista de las Antillas. Objetivos. Introducción a la Biología Molecular: células y cromosomas Discusión y repaso de Mitosis y Meiosis

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Chapter 2 Cellular Reproduction and Model Genetic Organisms

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  1. Chapter 2Cellular Reproduction and Model Genetic Organisms José A. Cardé-Serrano, PhD Biol 223 – Genética Universidad Adventista de las Antillas

  2. Objetivos • Introducción a la Biología Molecular: células y cromosomas • Discusión y repaso de Mitosis y Meiosis • Contraste de Procariotas y Eucariotas • Discusión de Sistemas Modelos para Genética.

  3. Chapter Outline • Cells and Chromosomes • Mitosis • Meiosis • Genetics in the Laboratory: An introduction to Some Model Research Organisms

  4. In both prokaryotic and eukaryotic cells, the genetic material is organized into chromosomes. Cells and Chromosomes

  5. The Cellular Environment • Cytoplasm—the inside of a cell • Water • Hydrophilic and Hydrophobic Molecules • Carbohydrates • Lipids • Proteins, including enzymes • Membrane—made of lipids and proteins • Nucleic acids • Organelles

  6. Prokaryotic and Eukaryotic Cells

  7. Animal and Plant Cells

  8. 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

  9. Vocabulary for Chromosomes • Diploid • Haploid • Polyploid and aneuploid • Somatic cells • Germ line • Gametes • Centromere • Telómero

  10. Cell Division in Prokaryotes: Fission • A mother celldivides to produce two daughter cells. • The mother cell’s chromosome is duplicated prior to fission. • Each daughter cell receives one copy of the chromosome. • Clone—a population of genetically identical cells. • Colony—a visible mass of cells.

  11. Cell Division in Eukaryotes:Mitosis and Cytokinesis

  12. Key Points • Cells, the basic units of all living things, are enclosed by membranes. • Chromosomes, the cellular structures that carry the genes, are composed of DNA, RNA, 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.

  13. Key Points • Haploid eukaryotic cells possess one copy of each chromosome; diploid cells possess two copies. • Prokaryotic cells divide by fission; eukaryotic cells divide by mitosis and cytokinesis. • Eukaryotic chromosomes duplicate when a cell’s DNA is synthesized; this event, which precedes mitosis, is characteristic of the S phase of the cell cycle.

  14. When eukaryotic cells divide, they distribute their genetic material equally and exactly to their offspring. Mitosis

  15. Microtubules and Centrioles • Spindle • Microtubule organizing centers (MTOCs) • Centrosomes and centrioles • Pericentriolar material • Aster

  16. Mitosis in Animal Cells

  17. Mitosis in Animal Cells

  18. Cytokinesis inAnimal and Plant Cells

  19. Key Points • 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)

  20. Key Points • 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.

  21. Sexual reproduction involves a mechanism that reduces the number of chromosomes by half. Meiosis

  22. Homologues

  23. Comparison ofMitosis and Meiosis

  24. Prophase I: Leptonema • Chromosomes condense • Each chromosome has two sister chromatids

  25. Prophase I: Zygonema • Synapsis of homologous chromosomes • Synaptonemal complex

  26. The Synaptonemal Complex

  27. Prophase I: Pachynema • Chromosomes condense further • Bivalent • Tetrad • Crossing over occurs

  28. Prophase I: Diplonema • Paired chromosomes separate slightly but are in contact as chiasmata

  29. Chiasmata

  30. Prophase I: Diakinesis • Nuclear envelope fragements • Spindle fibers attach to kinetochores • Chromosomes move to central plane in pairs

  31. Metaphase I • Paired chromosomes are oriented toward opposite poles • Terminalization: chiasmata move toward telomeres

  32. Anaphase I • Chromosome disjunction (separation of paired chromosomes) • Separated homologues move toward opposite poles

  33. Telophase I • Chromosomes reach the poles; nuclei forms • Spindle apparatus is disassembled • Daughter cells separated by membranes • Chromosomes decondensed • Each chromosome still has two sister chromatids

  34. Prophase II • Chromosomes condense • Chromosomes attach to a new spindle apparatus • Sister chromatids are attached to spindle fibers from opposite poles

  35. Metaphase II • Chromosomes align at equatorial plane

  36. Anaphase II • Centromeres split • Chromatid disjunction—sister chromatids move toward opposite poles

  37. 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

  38. Cytokinesis • The haploid daughter cell are separated by cytoplasmic membranes

  39. Daughter cells are NOT genetically identical • Maternal and paternal homologues synapse, then disjoin. • Different pairs disjoin independently. • Homologous chromosomes exchange material by crossing over

  40. Life Cycle ofSaccharomyces cerevisiae

  41. Life cycle ofNeurospora crassa

  42. Life Cycle of Plants:Alternation of Generations

  43. Oogenesis in Mammals

  44. Spermatogenesis in Mammals

  45. Key Points • 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.

  46. Key Points • In many organisms, the haploid products of meiosis develop directly into gametes. • In plants, the products of meiosis divide mitotically to form haploid gametophytes. • The gametophytic phase of a plant’s life cycle alternates with the sporophytic phase, which is diploid; meiosis occurs in the sporophyte.

  47. Geneticists focus their research on microorganisms, plants, and animals well suited to experimentation. Genetics in the Laboratory:An Introduction to Some Model Research Organisms

  48. Eschericia coli, a Bacterium • Rod-shaped bacterium • Molecular Genetics • 4.6  106 base pairs • 4288 protein-coding genes • Single circular chromosome • Bacteriophages

  49. Saccharomycescerevisiae,Baker’s Yeast • Unicellular fungus • 16 linear chromosomes • 12  106 base pairs • 6268 genes • Reproduces sexually and asexually • Model system por Genetics, Cell cycle, RNA studies

  50. Drosophila melanogaster,a Fruit Fly • Insect • Anatomically complex • 170  106 base pairs • 13,792 genes • Model system for Genetics, Develomental and Hox Genes

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