Lab #7 - Prelab Discussion_24

Lab #7 Overview

  • Title: Cellular Division & Asexual Reproduction in Various Organisms

  • Prelab Discussion by M. Weatherell, RIT

Lab Objectives

  1. Mitosis and Asexual Reproduction

    • Explain the relationship between mitosis and the processes in slime molds.

    • Consider how environmental changes (like food availability) alter these processes.

  2. Regeneration in Animals

    • Explore physical changes and timing of regeneration.

  3. Cell Cycle Activities

    • Describe activities of the cell cycle: what happens and when inside the cell.

    • Compare and contrast phases of mitosis and meiosis.

  4. Understanding Mitosis vs. Meiosis

    • Examine differences in plant and animal cell division.

Activities Today in Lab

  1. Activity #1 - Mitosis: The Real Thing

  2. Activity #2 - Comparison between Mitosis & Meiosis

  3. Activity #3 - Investigating Cellular Division & Chemotaxis in Physarum polycephalum

  4. Activity #4 - Cellular Regeneration in Platyhelminthes

Why Cell Division Occurs

  • Cell Theory: All cells come from pre-existing cells.

  • Repair and Replacement: Necessary for repairing worn-out cells in multicellular organisms.

  • Growth: Cell division is required for growth, increasing surface area to volume ratio.

  • Subdividing Cytoplasm: Divides the cytoplasm into smaller, membrane-bound units (cells).

  • Reproduction: Essential in both unicellular and multicellular organisms.

Prokaryotic Cell Division

  1. Stages of Division

    • Cell elongation

    • DNA replication

    • Formation of cross-wall

    • Cell separation

Eukaryotic Division Differences

  • Eukaryotes must divide their nucleus and organelles (mitosis or meiosis).

  • Genetic material replicates before nuclear division.

Eukaryotic Asexual Cell Division

  • Phases: G1 (growth), S (synthesis), G2 (final preparations), M (mitosis).

  • Duration: Approximately 24 hours to complete the cell cycle.

Chromosome Basics

  • Chromosomes: Units of genetic storage.

  • Diploid (2n): Two chromosome sets (e.g., human somatic cells - 46 chromosomes).

  • Haploid (n): One chromosome set (e.g., gametes - 23 chromosomes).

Chromosome Facts

  • Sister Chromatids: Identical copies of a chromosome.

  • Homologous Chromosomes: Paired chromosomes controlling the same trait but may have different alleles.

  • Sex Chromosomes: Determine genetic sex (XX = Female, XY = Male).

DNA Configuration

  • Interphase: Loose chromatin state for replication.

  • Mitosis: Super-coiled, visible chromosomes.

Phases of Eukaryotic Cell Cycle

Interphase

  • G1, S, G2 stages: Preparation for mitosis.

Mitosis

  • Phases: Prophase, Prometaphase, Metaphase, Anaphase, Telophase, and Cytokinesis.

Cytokinesis Differences

  • Animal Cells: Cleavage furrow formation.

  • Plant Cells: Formation of a cell plate.

Basics of Sexual Reproduction

  • Meiosis: Halves chromosome number for fertilization (2n to n).

    • e.g., In Humans: 46 (2n) cells to 23 (n) gametes.

  • Genetic Variation: Shuffling of genes results in genetically different gametes.

Meiosis Stages

  1. Meiosis I: Separation of Homologous Chromosomes - diploid to haploid.

  2. Meiosis II: Separation of Sister Chromatids - haploid remains haploid.

  • Interkinesis: No DNA replication occurs between meiosis I and II.

Comparing Eukaryotic Cellular Division

Similarities

  • Exists in all organisms (except viruses).

  • Both begin with diploid parent cells.

Differences

  • Mitosis creates diploid daughter cells; meiosis creates haploid.

Activity #1 – Mitosis Observations

  • Observe and draw phases of mitosis at 40X magnification.

  • Compare plant vs. animal cells during telophase.

Activity #2 – Mitosis & Meiosis Comparison

  • Utilize various resources to compare the two types of eukaryotic cell division.

Slime Molds Overview

  • Informal name for unrelated eukaryotic organisms; can live as single cells or aggregate into multicellular forms.

  • Two groups: Plasmodial and Cellular slime molds.

Why Slime Molds are Protists

  • Lack chitin in cell walls (a characteristic of fungi).

  • Exhibit amoeboid movement and have distinct life cycles, differing from fungi.

Plasmodial Slime Molds

  • Heterotrophic.

  • Feeding stage is a plasmodium (multi-nucleated cytoplasm).

  • Study of mitosis processes.

Chemotaxis Definition

  • Taxis: Movement in response to a stimulus.

  • Chemotaxis: Directed migration toward a chemical stimulus.

Activity #3 – Physarum Study

  • Observe Physarum under 400X magnification and document observations.

  • Investigate chemotaxis using oatmeal flakes as a stimulus.

Planaria Overview

  • Live in freshwater; exhibit negative phototaxis.

  • Asexual and sexual reproduction; model for tissue regeneration.

Regeneration Mechanism

  • Neoblasts: Planaria stem cells enabling regeneration by becoming necessary cell types.

Activity #4 – Planaria Regeneration

  • Cut planaria as per instructions; document observations.

Post Lab Clean-Up

  • Disposal protocols for lab materials and equipment.

Prelab Quiz Reminder

  • Complete Prelab Quiz #8 on macromolecules before next lab.

In this week's lab we will be exploring both mitosis and meiosis.

Questions Overview

  1. Mitosis only

  2. Meiosis only

  3. Both mitosis and meiosis

  4. Neither mitosis or meiosis

Prepared Slide Specimen Observation

For the prepared slide specimen, you are required to observe and draw/photograph the phases of mitosis under a compound microscope using Onion Root Tip or Whitefish Blastula.

Magnification Question

To estimate the duration of each phase of the cell cycle, you will observe fields of view at 400X magnification, which requires using the 40X objective lens since the eyepiece is 10X.

Slime Mold Species in Lab

We will be working with Physarum polycephalum in lab.

Chromosome Count in Plasmodial Stage

While in its plasmodial stage, the slime mold Physarum polycephalum has a Diploid number of chromosomes.

Chemotaxis Definition

Chemotaxis is best described as the directional movement of cells or organisms towards or away from a chemical stimulus.

Food Source for Slime Mold

The food source offered to the slime mold will be Oatmeal.

Group Classification of Planaria

Planaria belong to the group of organisms known as Flatworms.

Method to Anesthetize Planaria

In lab this week, the method to anesthetize the Planaria will be using Chlorobutanol.

Undifferentiated Cells in Planaria

Neoblast are the undifferentiated cells of flatworms that participate in the regeneration of lost parts.

Cell Division Overview

Mitosis Phase IdentificationThe image shows a cell in one of the phases of mitosis in both a plant and animal cell. In this phase, sister chromatids are being pulled apart by the mitotic spindles. This phase is known as Anaphase.

Question 2: Correct Order of Eukaryotic Cell CycleThe correct order of the stages of the eukaryotic cell cycle, starting with the phase where DNA replication/synthesis and growth occurs is:Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase/Cytokinesis.

Question 3: Mitosis Correct PairingThe pairing that is NOT correct for mitosis is:telophase--spindle appears.

Question 4: Correct Statements About MitosisThe statement that is NOT correct about mitosis is:During mitosis, the centromeres divide and the sister chromatids stay together.

Activity 2 - Cellular Division 101Question 6: Mitosis results in the creation of 4 haploid gamete cells is accurate for meiosis, whereas mitosis results in two identical daughter cells.

Question 7: Similar but not identical copies of duplicated chromosomes are known as Homologous chromosomes, while sister chromatids are two identical copies of genetic structures.

Differences Between Mitosis and Meiosis in AnaphaseIn anaphase of mitosis, sister chromatids are pulled apart to opposite sides. In anaphase I of meiosis, homologous chromosomes are separated, and in anaphase II, sister chromatids are pulled apart in haploid cells.

Slime Molds vs. FungiQuestion 9: The true statement regarding the difference between fungi and slime molds is:Slime molds have a distinct life stage called a plasmodium, which is a large, multinucleated mass of cytoplasm that can move and engulf food—a feature not seen in fungi.

Feeding Behavior of PhysarumDuring the laboratory experiment with slime molds, when food is presented in one spot, Physarum may grow more towards that area. If food is spread out, it will grow to different locations where the food is available.

Primary Stimulus Triggering Regeneration in PlanariaThe primary stimulus that triggers regeneration in a planarian is:Tissue damage or amputation.

Totipotent Cells in PlanariaQuestion 13: The statement is:True. Neoblasts are capable of regenerating any part of the planarian.