Podcast
Questions and Answers
What is the primary function of cytokinesis in the cell cycle?
What is the primary function of cytokinesis in the cell cycle?
Which phase of mitosis involves the chromosomes being at their greatest condensation?
Which phase of mitosis involves the chromosomes being at their greatest condensation?
Which structure forms and attaches to centromeres during prophase?
Which structure forms and attaches to centromeres during prophase?
What is the main distinction between mitosis and meiosis?
What is the main distinction between mitosis and meiosis?
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During which phase do homologous chromosomes separate in meiosis?
During which phase do homologous chromosomes separate in meiosis?
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What term is used to describe the exchange of genetic material between homologous chromosomes?
What term is used to describe the exchange of genetic material between homologous chromosomes?
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In which phase of meiosis do sister chromatids separate?
In which phase of meiosis do sister chromatids separate?
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What is the purpose of the centrosome during mitosis?
What is the purpose of the centrosome during mitosis?
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What is the primary purpose of meiosis in sexually reproducing organisms?
What is the primary purpose of meiosis in sexually reproducing organisms?
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What is a key difference between mitosis and meiosis?
What is a key difference between mitosis and meiosis?
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What role does crossing over play during meiosis?
What role does crossing over play during meiosis?
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During which phase of meiosis does independent assortment occur?
During which phase of meiosis does independent assortment occur?
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How many daughter cells are produced at the end of meiosis?
How many daughter cells are produced at the end of meiosis?
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What type of cells does mitosis produce?
What type of cells does mitosis produce?
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During which stage of meiosis does homologous chromosomes separate?
During which stage of meiosis does homologous chromosomes separate?
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Which statement accurately describes gametes?
Which statement accurately describes gametes?
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What is the result of independent assortment during meiosis?
What is the result of independent assortment during meiosis?
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During which phase of meiosis does crossing over occur?
During which phase of meiosis does crossing over occur?
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What is the key difference between meiosis and mitosis?
What is the key difference between meiosis and mitosis?
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How many haploid cells are produced at the end of meiosis?
How many haploid cells are produced at the end of meiosis?
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Which phase of meiosis is characterized by the separation of homologous chromosomes?
Which phase of meiosis is characterized by the separation of homologous chromosomes?
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What structures form during synapsis in Prophase I of meiosis?
What structures form during synapsis in Prophase I of meiosis?
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What aspect of meiosis reduces genetic material to haploid cells?
What aspect of meiosis reduces genetic material to haploid cells?
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What happens during Metaphase II of meiosis?
What happens during Metaphase II of meiosis?
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In which cycle do gametes undergo fertilization to form a zygote?
In which cycle do gametes undergo fertilization to form a zygote?
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What is the end product of meiosis II?
What is the end product of meiosis II?
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What occurs during Telophase I of meiosis?
What occurs during Telophase I of meiosis?
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Which of the following statements accurately describes crossing over?
Which of the following statements accurately describes crossing over?
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What marks the end of meiosis II?
What marks the end of meiosis II?
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Study Notes
Lab 12: Mitosis and Meiosis
- The lab focuses on the processes of mitosis and meiosis
- The lab manual's page numbers are 71-75 for Fall 2024
- The Amoeba Sisters, created a cartoon of Paramecium to illustrate the concept of Mitosis.
- The goals of the lab include understanding differences and similarities between mitosis and meiosis
- Learning the phases of mitosis in plant and animal cells
- Describing differences in mitotic processes between plant and animal cells
- Understanding the concept of crossing-over
Goals of this Lab
- Understand the distinctions and commonalities between mitosis and meiosis
- Identify the stages of mitosis in cells
- Recognize the differences in mitosis between plant and animal cells
- Grasp the significance of crossing-over
Todays Activities
- Modeling the cell cycle using colored beads
- Observing mitosis in plant cells (prepared root tip slides)
- Observing mitosis in animal cells (prepared whitefish blastula slides)
- Modeling meiosis using colored beads
- Observing meiosis in Sordaria (determining if ascocarp display crossing-over)
Mitosis vs. Meiosis
- Mitosis is a part of the cell cycle
- Mitosis generates two genetically identical cells
- Mitosis occurs when an organism grows or worn out cells need to be replaced
- Meiosis is found in the life cycle of organisms that reproduce sexually.
- Meiosis reduces diploid chromosome numbers by half, making them haploid
Chromosomes
- Genome: the complete collection of genetic information in a cell.
- DNA can exist as chromatin (DNA and histone protein complex) or as highly condensed chromosomes.
- Chromosomal number varies among organisms. Humans have 46 chromosomes in somatic cells.
- Somatic cells (non-reproductive cells) contain homologous chromosome pairs.
- Gametes (reproductive cells like sperm and ova) have half the number of chromosomes as somatic cells—they are haploid.
Homologous Chromosomes
- Homologous chromosomes have similar size, shape, centromere location, and hereditary information (for the same traits).
- Information from the mother and father varies.
Eukaryotic Cell Cycle: Two Major Phases
- Interphase lasts about 90% of the cell cycle and involves growth, metabolic processes, and duplication of DNA and cytoplasm.
- The Interphase includes G1—first gap, S—synthesis, and G2—second gap—phases.
- Mitotic phase (M phase), mitosis—nuclear division— and cytokinesis separate and divide the cytoplasm into two cells
M phase - Two Major Events
- Mitosis involves the division of the nucleus, splitting of sister chromatids, and a continuous process, described in five distinct subphases (prophase, prometaphase, metaphase, anaphase, and telophase).
- Cytokinesis—the cytoplasm division—splits the two daughter cells
How the Cell Cycle Works
- Interphase—G1, S, and G2—prepares the cell for division.
- Mitosis (M phase) involves prophase, metaphase, anaphase, and telophase phases. This phase sees chromosomes condense, line up at the center of the cell, and separate to opposite poles, followed by nuclear envelope reformation.
- Cytokinesis involves dividing the cytoplasm in two, resulting in two daughter cells
Exercise 7.1: Modeling the Cell Cycle and Mitosis in an Animal Cell
- Students use pop beads and magnetic centromeres to model the stages of the cell cycle and mitosis.
- Learning phases include interphase, mitosis (prophase, prometaphase, metaphase, anaphase, and telophase), and cytokinesis.
Prophase
- First stage of mitosis: chromosomes condense, the nuclear envelope and nucleolus disappear, and the mitotic spindle begins to form.
- Spindle fibers extend from poles toward chromosomes' centromeres, attaching at kinetochores.
- In animal cells, centrosomes (with centriole pairs) migrate to opposite poles.
Prometaphase
- Nuclear envelope disassembles, chromosomes reach maximum condensation and spindle fibers attach to kinetochores on each chromosome.
Metaphase
- Spindle apparatus fully assembled.
- Centromeres of all chromosomes line up along the spindle's equator (metaphase plate).
Anaphase
- Centromeres split, separating sister chromatids.
- Daughter chromosomes pulled to opposite poles of the elongating spindle.
Telophase
- Chromosomes decondense, spindle apparatus disintegrates.
- Nuclear membranes reform around each set of unduplicated chromosomes.
- Nucleoli reform
Cytokinesis
- Cytoplasm divides.
- In animal cells, a cleavage furrow forms, pinching the cell into two daughter cells.
- In plant cells, a cell plate forms midway between the two nuclei, eventually developing into a new cell wall.
Exercise 7.2: Observing Mitosis and Cytokinesis in Plant Cells
- Students observe prepared onion root tip slides to identify different phases of mitosis (interphase, prophase, prometaphase, metaphase, anaphase, telophase), and cytokinesis.
Allium (onion) root tip
- Prepared slides showing various stages of the cell cycle, including interphase, prophase, prometaphase, metaphase, anaphase and telophase , cytokinesis.
Whitefish Blastula
- Prepared slides showcasing various stages of the cell cycle in animal cells, specifically interphase, prophase, metaphase, anaphase, and telophase and cytokinesis.
Exercise 7.3: Observing Chromosomes, Mitosis, and Cytokinesis in Animal Cells
- Identify phases by observing whitefish blastula slides
- Understand phases of mitosis and cytokinesis in animal cells
- Compare animal and plant cell mitosis differences
Meiosis and the Life Cycle of Sexually Reproducing Organisms
- Meiosis is part of sexual reproduction.
- Meiosis involved in various ways in the life cycle of multicellular eukaryotes (fungi, plantae, and animalia), where meiosis and fertilization happens at different times.
The Stages of Meiosis
- Meiosis consists of two successive nuclear divisions (meiosis I and meiosis II).
- Meiosis I separates homologous chromosomes.
Crossing over
- Occurs between two non-sister chromatids in homologous chromosomes. (During synapsis phases)
- Sections of exchanged segments happen
- Chiasma: the X-shaped areas where genetic segments swap
Prophase I
- Similar to mitosis prophase except for synapsis and tetrad creation
- Homologous chromosomes align and form a tetrad structure, allowing crossing-over.
Metaphase I
- Tetrads align on the metaphase plate
- Random orientation of homologues results in different combinations in the gametes.
Anaphase I
- Homologous chromosomes separate and move to opposite poles.
- Sister chromatids stay attached.
Telophase I
- Chromosomes arrive at opposite poles, the nuclear envelope might reform, and cytokinesis may occur. The cell is now haploid.
Prophase II
- Similar to mitosis prophase
- Spindle fibers from chromosomes clusters/pairs
Metaphase II
- Similar to metaphase in mitosis: spindle fibers bind to each sister chromatid, individual chromosomes align at the metaphase plate
Anaphase II
- Similar to anaphase in mitosis
- Sister chromatids separate and move to opposite poles
Telophase II
- Similar to telophase in mitosis
- Chromosomes decondense
- Nuclear envelopes reform.
- Cytokinesis occurs, resulting in four haploid cells.
A Comparison of Mitosis and Meiosis
- Mitosis produces two identical diploid cells. Meiosis produces four genetically diverse haploid cells.
- Meiosis includes synapsis and reduction division, which mitosis does not.
Exercise 7.4 Modeling Meiosis
- Use pop beads to demonstrate meiosis stages, including crossing over
Sordaria
- Ascomycete fungus, spending most of its life cycle as a haploid.
- Two 2n strains fuse to form a zygote
- Then eight haploid cells (ascospores) are formed through meiosis and mitosis.
Spore formation and Crossing Over
- Observing how the color of spores in an ascus can demonstrate if crossing over has occurred between homologous chromosomes.
Exercise 7.5 Meiosis in Sordaria Fimicola
- Study of crossing-over in Sordaria images
- Complete the associated discussion questions and tables
- Focus on chiasma, sordaria, ascus, and ascospores
Parental and Crossover Phenotypes
- Images showing the arrangement of ascospores in asci (sacs) with regards to different phenotypes, to examine if crossing over happened.
Crossing over ?
- Analysis of ascus patterns to determine if crossing over occurred during meiosis, noting the possible outcomes (No crossing over, Yes, Maybe).
- Students evaluate ascus patterns using diagrams of meiotic products or real images.
Summary of Outputs
- Post-lab tasks are to be found on Blackboard.
- For notebooks, pictures from exercises 7.2 and 7.3 should be included, questions addressed, and tables (7.1 and 7.2) completed. Also, review your knowledge.
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Description
This lab focuses on the processes of mitosis and meiosis, highlighting their distinctions and commonalities. Students will learn about the stages of mitosis in both plant and animal cells, as well as the significance of crossing-over. Activities include modeling the cell cycle and observing mitosis in prepared slides.
