Lab 12 Mitosis & Meiosis (MK) Fall 2024 PDF

Lab 12: Mitosis and Meiosis 7.1-7.5 Fall 2024 Lab Skills 10:30 section 12:30 section Oct 28 (Mon) 20 min long Lab Skills (cont.) the students get a 20 minute time slot to come to lab where they will randomly be assigned a station. Th...

Lab 12: Mitosis and Meiosis 7.1-7.5 Fall 2024 Lab Skills 10:30 section 12:30 section Oct 28 (Mon) 20 min long Lab Skills (cont.) the students get a 20 minute time slot to come to lab where they will randomly be assigned a station. The Stations all have identical procedures that need to be performed, but they have slightly different materials (either the solution is different or the microscope slides are different) Lab Skills (cont.) Questions (a total of 4 questions) 1. Microscopy (2 questions)  identifying the images on the slides (using compound) 2. Pipetting & Weighing (1 question)  Transferring a volume of solution & weighing it using a balance (taring) 3. Spectrophotometry  Measuring either absorbance/transmittance at different WV (know how to blank; change the mode) Lab Report The topic will be “Photosynthesis,” specifically covering exercises LM6.3 and 6.4 that you performed in class. Review Lab 10 PowerPoint on Scientific Writing. Rubric and example reports will be provided The required sections are as follows: (Please do not include an “Abstract” section.) 0. Lab Report Cover 1. Introduction 2. Materials and Methods 3. Results 4. Discussion 5. References Due dates  Nov. 8 (FRI): First Draft due  Nov. 11 (MON): Returned with feedback  Nov. 22 (FRI): Final Draft due Submission: Google drive (as google doc/ MS word) https://drive.google.com/drive/folders/1qGTJ5KNGlz8Enlhj8vIahIHQNcjjhNf2?usp=drive_link  Goals of this lab Concepts Outputs Understand the differences and Used models to learn the steps of similarities between mitosis and meiosis mitosis and meiosis Identify the phases of mitosis in cells Found both plant and animal cells in all stages of mitosis under a microscope, Describe the mitotic differences between and drawn pictures of all the stages plant and animal cells Understand the importance of crossing over  Mitosis vs. Meiosis Mitosis Meiosis Is part of the cell cycle Is found in the life cycle of sexually reproducing organisms Generates two genetically identical cells Reduces diploid chromosome numbers by half (makes them haploid) Carried out when an organism grows in size or when worn out cells need to be replaced  Chromosomes Genome: the complete collection of all the genetic information of a cell (genes + non- genic regions) DNA can exist as chromatin (DNA and histone protein complex) or in the form of chromosomes (highly condensed chromatin, coiled to fit into small spaces). Chromosomal number varies among organisms: most eukaryotes have 10-50 in their somatic (non-reproductive) cells  e.g. Human (23n=46), Chimpanzee (24n=48), Apple (17n=34), Hermit crab (127n=254), Indian muntjac deer(1n=2) Chromosomes occur in pairs of homologous chromosomes (or homologues) in somatic cells, making them diploid cells (2n) Gametes: reproductive cells (sperm and ova) with half as many chromosomes as somatic cells, making them haploid (n). Chromatin vs. Chromosome Homologous Chromosomes Homologous chromosomes, or A pair of homologues (homologous chromosomes) homologues, have similar: Size Shape Centromere location Hereditary information (for the same A gene locus traits and situated in the same relative chromosomal location). A pair of alleles Homologues carry information on the same traits, but the information may vary (one is Three pairs of genes inherited from the mother, one from the father).  Eukaryotic cell cycle: two major phases Interphase Mitotic Phase (M phase)/ Cell Division Occupies 90% of the cell cycle, is the stage where a cell: A microtubular apparatus, known as the Grows in size & mass mitotic spindle, forms and binds to the Undergoes metabolic reactions replicated DNA organized into Duplicates its DNA & cytoplasm chromosomes Prepares for mitosis The spindle moves them apart, giving rise Usually the longest part of the cycle. Can be to two cells with identical genetic divided into subphases: information G1 phase (“first gap”) – Cell grows in size and undergoes normal metabolic activities S phase (“Synthesis”) – DNA replicated/synthesized, G2 phase (“second gap”) – The cell prepares for mitosis/cell division Eukaryotic cell cycle: two major phases Interphase  Chromosomes during the cell cycle During the G1 phase, each chromosome is a single structure, with a single centromere During the S phase each of the homologous chromosomes undergo replication, forming two identical copies called sister chromatids, joined together by a single centromere, and will be separated during division Centromeres are the narrow “waist” of the duplicated chromosome where the two chromatids are most closely attached. Humans have 23 pairs of homologous chromosomes. CHROMOSOME STRUCTURE  M phase- two major events Mitosis Cytokinesis Division of the nucleus Division of the cytoplasm Consists of the separation of the sister Consists of the partition of two chromatids cytoplasms of the two daughter cells A continuous process, but described in five distinct subphases: ○ Prophase ○ Prometaphase ○ Metaphase ○ Anaphase ○ Telophase How the cell cycle works Exercise 7.1: Modeling the cell cycle and mitosis in an animal cell. You will use pop-beads Key terms: and magnetic Haploid/Diploid centromeres to model Homologous the following stages of Chromosomes the cell cycle and Nuclear Envelope mitosis: Chromatin Interphase Centrosome M-phase Centrioles Mitosis Nucleoli Prophase Sister Chromatids Prometaphase Spindle Metaphase Kinetochores Anaphase Chromosomes Telophase Cleavage Cytokinesis Furrow/Cell Plate  Prophase First subphase of mitosis: chromosomes condense, nuclear envelope begins to disintegrate, and the nucleolus disappears. Mitotic spindle begins to form: cables made of microtubules, extending from poles towards the centromeres of chromosomes Will continue to extend until attached to a centromere at a protein disc calle a kinetochore. In animal cells, this is facilitated by centrosomes (w/ the centriole pairs) after they’ve migrated to opposite ends/poles of the cell (no assistance needed for plant cells).  Prometaphase Nuclear envelope is disassembled. Chromosomes are at their greatest condensation. Each duplicated chromosome contains two kinetochores in its centromere region, which face in opposite directions A spindle fiber attaches each kinetochore to an opposing pole of the spindle Non-kinetochore fibers from opposite poles overlap and interact at the spindle equator  Metaphase The spindle apparatus is completely assembled. The centromeres of all the chromosomes are lined up at the spindle’s equator. Each of the chromosomes has one sister chromatid located on either side of the equator, creating the metaphase plate.  Anaphase The centromeres, which join the sister chromatids together, separate. When this occurs, sister chromatids of each chromosome are pulled apart, becoming daughter chromosomes. The daughter chromosomes move to the opposing poles of the spindle, which lengthens.  Telophase Chromosomes decondense. Spindle apparatus disintegrates. Two nuclear membranes form, one around each set of unduplicated chromosomes. These nuclear membranes are formed from remnants of the mother cell nuclear envelope and other components of the endomembrane system. Nucleoli reform.  Cytokinesis Occurs at the end of mitosis (during B anaphase and telophase) and is a division of the cytoplasm into roughly equal halves. Falls in the “M” phase, but not A technically a subphase of mitosis. The mechanism of cytokinesis differs between animal (A) and plant (B) cells.  Cytokinesis Animal Cells Plant cells Occurs by actin filaments contracting and A new cell wall is laid down at a right pinching the cell in two. angle to the mitotic spindle to divide the two daughter cells: this is the cell plate. Evident as a cleavage furrow that Cellular vesicles enclosing pectins appears between the daughter cells. derived from the golgi body come together at the spindle’s equator. A band of actin filaments is located on the inside of the cell membrane at the Cellulose fibers are produced among spindle’s equator: this constricts when the the pectins leading to the formation of myosin motor proteins bind the the cell plate, and eventually the cell microfilaments tighter. wall.  Animal cell cytokinesis Microtubules and actin-myosin communicate with each other to coordinate the cleavage plane and initiate furrowing. Furrowing based on contraction of the contractile ring, a bundle of aligned actin filaments alternating with myosins. Animal cells determine the furrow region in relation to the position and orientation of the mitotic apparatus.  Plant cell cytokinesis In terrestrial plants, cytokinesis occurs by cell plate formation. This involves the delivery of golgi-derived vesicles to the equator of the cell and the subsequent fusion of these vesicles with each other.  Results of Mitosis Two daughter nuclei. Each with the same chromosome number as parent cell. Chromosomes in unduplicated form (to be replicated).  Exercise 7.2: Observing mitosis and cytokinesis in plant cells Using prepared slides of onion (Allium) root tips, you will look for cells in each phase of mitosis. Draw all of the following phases: Interphase M phase Mitosis Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis  Allium (onion) root tip, L.S., 40X & 100X Dr. Iwantsch Fordham University  Allium interphase, L.S., 400X Dr. Iwantsch Fordham University  Allium prophase , L.S., 400X Dr. Iwantsch Fordham University  Allium prometaphase , L.S., 400X Dr. Iwantsch Fordham University  Allium metaphase, L.S., 400X Dr. Iwantsch Fordham University  Allium anaphase, L.S., 400X Dr. Iwantsch Fordham University  Allium telophase , L.S., 400X Dr. Iwantsch Fordham University  Allium cytokinesis, L.S., 400X Dr. Iwantsch Fordham University  Exercise 7.3: Observing chromosomes, mitosis and cytokinesis in animal cells Locate and draw all the following phases: Interphase M phase Mitosis Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis What are the differences between mitosis in animal and plant cells?  Whitefish blastula, section, 40 & 100X Dr. Iwantsch Fordham University  Whitefish interphase, section, 400X Dr. Iwantsch Fordham University  Whitefish prophase, section, 400X Dr. Iwantsch Fordham University  Whitefish metaphase, section, 400X Dr. Iwantsch Fordham University  Whitefish anaphase, section, 400X Dr. Iwantsch Fordham University  Whitefish telophase, section, 400X Dr. Iwantsch Fordham University  Whitefish cytokinesis, section, 400X Dr. Iwantsch Fordham University  Meiosis and the life cycle of sexually reproducing organisms The alternation of meiosis and fertilization is found in all sexually reproducing organisms (mechanism that preserves chromosome number). Meiosis is involved in extremely different ways in the life-cycle of multicellular eukaryotes: Fungi Plantae Animalia Organisms belonging to each of these kingdoms show differences in respect to the timing of meiosis and fertilization.  Meiosis in animals vs plants Animals Plants Only in germ cells (2n), which give rise to Only in the gametangia (specialized gametes (n). structures located in the adult sporophyte), where sporocytes (2n) generate spores At sexual maturity, testes and ovaries (n) generate haploid gametes via meiosis. Spores germinate, go through many rounds During fertilization, gametes fuse to form of mitosis, produce the gametophyte the zygote (2n), which further divides by generation (n), which produce haploid mitosis, becoming a multicellular gametes via mitosis organism. At fertilization (fusion of gametes), the Somatic (2n) cells contain two sets of sporophyte zygote (2n) is made and chromosomes: one from a sperm cell (n) undergoes many rounds of mitosis to and one from an egg cell (n). produce an adult sporophyte.  Key Fig. 13-6a Haploid (n) Diploid (2n) n Gametes n n MEIOSIS FERTILIZATION Zygote 2n 2n Diploid multicellular Mitosis organism (a) Animals Key Fig. 13-6b Haploid (n) Diploid (2n) Haploid multi- cellular organism (gametophyte) Mitosis n Mitosis n n n n Spores Gametes MEIOSIS FERTILIZATION 2n 2n Diploid Zygote multicellular Mitosis organism (sporophyte) (b) Plants and some algae  The stages of meiosis Two successive nuclear divisions: meiosis I and meiosis II Meiosis I Meiosis II DNA is replicated only once Preceded by brief interphase, no DNA replication beforehand Separates replicate sister chromatids (non-identical Separates the homologous pairs because of the crossing over in meiosis I) Results in two haploid cells A mitotic division of the products of meiosis: results in four haploid cells overall Stages: Prophase I Stages: Metaphase I Prophase II Anaphase I Metaphase II Telophase I Anaphase II Telophase II  Crossing over Occurs between two non-sister chromatids of homologous chromosomes (attracted by synapsis) The chromatids break in the same place Sections of chromosomes are exchanged The result is a hybrid chromosome Chiasmata: X-shaped areas where segments of the homologous chromosomes have swapped genetic information  Prophase I Similar to prophase in mitosis, except: Synapsis-duplicated homologous chromosomes line up together as a pair, forming a tetrad: a complex containing two pairs of sister chromatids  Metaphase I Similar to metaphase in mitosis, except: Homologous chromosomes line up at the equator of the spindle as tetrads, by random orientation: The individual homologues randomly face different poles, resulting in gametes with different combinations of parental chromosomes This process is called independent assortment:  Anaphase I Similar to anaphase in mitosis, except: Reduction division takes place (2N→ N) Homologous pairs separate and individual homologues move to each pole The centromere does not split, and the sister chromatids remain attached Each daughter cell gets both sister chromatids of one of the members of each homologous chromosome pair  Telophase I Similar to telophase in mitosis except: Some events might not go to completion, since the cell has a brief interphase and then immediately begins meiosis II Cytokinesis produces two haploid cells (N)  Prophase II Similar to prophase in mitosis: New spindle forms to attach to chromosome clusters  Metaphase II Similar to metaphase in mitosis: Spindle fibers bind to both sides of the centromere Individual chromosome align along central plane  Anaphase II Similar to anaphase in mitosis: sister chromatids move to opposite poles  Telophase II Similar to telophase in mitosis: Nuclear membrane reforms Nucleoli reappear Spindle apparatus disassembles Chromosomes decondense After cytokinesis, we are left with four haploid (n) daughter cells  Exercise 7.4: Modeling Meiosis Use pop beads to model the steps of the cell Key Terms: cycle and meiosis, including crossing over. Meiosis I Meiosis II Complete table 7.1 (Postlab 12) Synapses Tetrad Crossing over Chiasma Alleles  A comparison of mitosis and meiosis Meiosis has two unique features not found in mitosis: Synapsis The process of drawing together homologous chromosomes down their entire lengths so that crossing over can occur Reduction division Meiosis involves two nuclear divisions but only one DNA replication, the final amount of genetic material passed to the gametes is halved.  Spore formation and crossing over Sordaria– Ascomycete fungus, spends most of its life cycle as a haploid. After, two 2n strains (each w/ a different allele for spore color), fuse to form 2n zygote. Zygote then forms two haploid strains (n), and undergoes meiosis I, meiosis II, and one round of mitosis (eight haploid cells). Since the cells (spores) are haploid, genotype = phenotype. The allele of their spore color gene can therefore be determined visually. If crossing over: the phenotypic sequence of spore color changes. If no crossing over: four ascospores on one each side of the ascus will be the same color. Ascus Ascus- a sac containing eight linearly distributed cells (ascospores), the end results of meiosis and one round of mitosis. We will be analyzing the organization of the spores within the asci. Sordaria life cycle  Exercise 7.5: Meiosis in Sordaria fimicola: a study of crossing over You will visual crossing over looking at images of Sordaria. Complete discussion questions and Table 7.2. Key terms: Chiasma, Sordaria, Ascus Ascocarp Ascospores  Parental and Crossover Phenotypes: (a) All one color (tan) (b) All one color black (c) Non-crossing over (d) Crossing over (e) Crossing over Exercise 7.5: Meiosis in Sordaria fimicola: a study of crossing over Crossing over? NO YES YES MAYBE  Summary of Outputs Postlab Notebook Make flashcards of all important terminology! Pictures for 7.2, 7.3 Submit the definitions to blackboard Questions throughout the exercises in your own words. Table 7.1, 7.2 Reviewing your knowledge