1 / 31

Rationale:

Lab 8: Mitosis, Meiosis, and Chromosomes. Rationale: We will investigate the processes wherein cells produce genetically identical daughter cells and the mechanisms of heredity and variation within organisms. Purpose of Lab 8 exercises:. ID stages of mitosis and meiosis

bridgeway
Download Presentation

Rationale:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lab 8: Mitosis, Meiosis, and Chromosomes Rationale: We will investigate the processes wherein cells produce genetically identical daughter cells and the mechanisms of heredity and variation within organisms

  2. Purpose of Lab 8 exercises: • ID stages of mitosis and meiosis • Locate the stages of mitosis on an onion root tip • Find and describe the stages of meiosis in lily anthers • Describe polytene chromosomes isolated from Drosophila

  3. Somatic vs. Reproductive Cells SOMATIC CELLS Are all body cells except reproductive cells Characteristics Diploid 2 copies of each chromosome e.g. Humans: = 46

  4. Somatic vs. Reproductive Cells REPRODUCTIVE CELLS (GAMETES) Female gametes: eggs (ova) Male gametes: sperm Characteristics Haploid1 copy of each chromosome e.g.) Humans = 23

  5. Chromosomes and Genes • Chromosome Long strand of DNA and associated proteins • Chromatin Complex of DNA and protein • Gene Discrete unit of heredity Specific nucleotide sequence • Locus Physical location of a gene on a chromosome

  6. MITOSIS • Biological significance: • The common mechanism in eukaryotes for partitioning the genetic material equally at cell division.

  7. The Cell Cycle Centrioles replicate

  8. The Cell Cycle Interphase- 75% of cell life cycle G1: rapid growth S: DNA replicates ; centrioles replicate. G2: cell prepares for cell division; microtubular structures form.

  9. The Cell Cycle Cell Division Mitosis: cell divides its nuclear components (chromosomes). Cytokinesis: cell divides its cytoplasmic components.

  10. 4 Phases of Mitosis Prophase Metaphase Anaphase Telophase

  11. Interphase

  12. Prophase Early centrioles

  13. Prophase late

  14. Metaphase

  15. Anaphase

  16. Telophase

  17. Cytokinesis cleavage furrow

  18. Experiment 1: Mitosis in the Onion Root Tip • Examine onion root tip • Identify the 4 different phases of mitosis Region with high cell division Root tips: • Useful because cells are frequently dividing • Use the very tip of the root Apical meristem Root cap

  19. Difference between Meiosis and Mitosis

  20. Meiosis • Follow behavior of chromosomes through sexual cycles • Makes gametes haploid • Gametes only cells in human body not produced by mitosis

  21. Stages of Meiosis Meiosis I and Meiosis II 4 stages leading up to the cell divisions These stages are called prophase, metaphase, anaphase, and telophase Prophase I Prophase II Metaphase I Metaphase II Anaphase I Anaphase II Telophase I Telophase II

  22. Meiosis I Interphase Prophase I Metaphase I Anaphase I Telephase I

  23. Meiosis II Prophase II Metaphase II Anaphase II Telephase II

  24. Meiosis: Prophase I & Metaphase I Chromatin condenses into discrete chromosomes Homologous chromosomes pair up—crossing over can occur: genetic diversity Metaphase plate Spindle fibers from each pole attach to one chromosome of each homologue Chromosomes align on the metaphase plate as homologous pairs Spindle fibers

  25. Meiosis: Anaphase I The 2 chromosomes of each homologous pair separate Move toward opposite poles Haploid The chromosomes moved to opposite poles Cytokinesis separates the cytoplasm into 2 daughter cells Each cell is haploid Haploid

  26. Meiosis: Prophase II The chromatin again condenses into chromosomes The chromosomes align on the metaphase plate

  27. Meiosis: Anaphase II Sister chromatids separate Move toward opposite poles Sister chromatids are now individual chromosomes Haploid Haploid Nuclei begin to form at opposite poles Cytokinesis occurs Haploid Haploid 4 Haploid daughter cells

  28. Experiment 2: Meiosis in the Lily Anther Today: Look at prepared slides of Lily Anther Male reproductive organ where meiosis occurs Pollen grains (gametes) are haploid Very thin cross-section of stained lily anther

  29. Meiosis in the Lily Anther Each anther contains 4 pollen sacs Look at cells in pollen sacs Pollen grains will be in different stages of meiosis

  30. Experiment 3: Polytene Chromosomes of Drosophila Today: Examine prepared slides of polytene chromosomes found in Drosophila melanogaster (fruit fly) Located specifically in: • The gut. • Malphigian tubules (excretory organs) of larvae. • Footpads of adults. • Salivary glands of larvae

  31. Polytene Chromosomes of Drosophila Giant chromosomes Have undergone many rounds of DNA duplication without cell division • Large size • Easily visible under the compound light microscope • Amenable for various genetic studies

More Related