Cell Division Mitosis vs Meiosis Human Biology By

Cell Division: Mitosis vs. Meiosis Human Biology By: Carly Case

Mitosis Animation l l The video illustrates the steps of Mitosis. http: //www. youtube. com/watch? v=BFWel. OJ 7 f. W 0

Mitosis: Interphase l Cell preparing for mitosis – l l l Metabolic activity Chromosomes not clearly defined Nucleolus may be visible (dark spot) May contain centrioles: organizational site for microtubules

Mitosis: Prophase l l Chromosomes are visible via light microscope Nucleolus disappears Centrioles move to opposite ends of cell Fibers extend from centromeres – Some fibers form the mitotic cpindle

Mitosis: Prometaphase l l Nuclear membrane dissolves Proteins attach to the centromeres creating kinetochores Microtubules attach at kinetochores Chromosomes begin moving

Mitosis: Metaphase l l Spindle fibers align chromosomes along the middle of the cell nucleus (AKA metaphase plate) By aligning in the middle, it ensure the chromosomes will separate in Anaphase

Mitosis: Anaphase l l Paired chromosomes separate at kinetochores Chromosomes move to opposite sides of cell

Mitosis: Telophase l l Chromatids arrive at opposite poles of cell New membranes form around daughter nuclei Chromosomes are no longer visible under light microscope Sprindle fibers disperse

Mitosis: Cytokinesis l Occurs in Animal cells – – Fiber ring composed of protein (known as Actin) pinches the cell into TWO daughter cells Each daughter cell has one nuclei l Occurs in Plant Cells – Cell plate is synthesized between TWO daughter cells

Meiosis l l l Type of cell division where germ cells (eggs and sperms) are produced Involves a reduction in the amount of genetic material Single parent diploid cell divides to produce FOUR daughter HAPLOID cells

Meiosis: Interphase l l Preparation for meiosis to begin Chromosomes are duplicated Two centrosomes serve as microtubule organizing centers Microtubules extend from centrosomes to form an Aster

Meiosis: Prophase l l l Crossing Over occurs Nucleolus disappears Mitotic spindle forms between two pairs of centrioles Nucleur envelope disappears Prophase I consumes 90% of the two divisions

Meiosis: Metaphase I l l l Centrioles at opposite poles of cell Chromosomes align on metaphase plate Spindle fibers from one pole of cell attach to one sister chromatid. Spindle fibers from other pole of cell attach to other sister chromatid

Meiosis: Anaphase I l Two chromosomes separate by moving toward opposite poles

Meiosis: Telophase I l l l One haploid SET of chromosomes at each pole Nucleur envelope reforms around each chromosome set Cytokinesis follows by pinching the cell into two cells.

Meiosis: Prophase II l l No new chromosome replication occurs Centrioles duplicate Nuclear envelope breaks down Spindle apparatus forms

Meiosis: Metaphase II l l Each daughter cells completes the formation of the spindle apparatus Single chromosomes align on metaphase plate

Meiosis: Anaphase II l l Centromeres separate The two chromatids of each chromosome move to opposite poles

Meiosis: Telophase II l l l Nuclear envelope forms around each set of chromosomes Cytokinesis takes place FOUR daughter cells with a HAPLOID set of chromosomes are produced

Meiosis Vs. Mitosis l l l One set of stages Produces TWO daughter cells Each daughter cell has their own nuclei l l l Two sets of stages Produces FOUR daughter cells Each daughter cell is HAPLOID

Factors that affect the cell cycle l l l Metabolic factors Intrinsic molecules inside the cytoplasm Interaction with other cells

Further Investigation l l l Visit the sites below for an interactive experience with Mitosis and Meiosis. http: //www. cellsalive. com/mitosis. htm http: //www. phschool. com/science/biology_pla ce/biocoach/meiosis/intro. html

References l l l Cells Alive. http: //www. cellsalive. com/mitosis. htm Mitosis. http: //www. biology. arizona. edu/cell_bio/tutori als/cell_cycle/cells 3. html Meiosis. http: //www. phschool. com/science/biology_pla ce/biocoach/meiosis/intro. html