Mitosis 2020 PDF

Aim: How do cells reproduce? Do Now: Why is reproduction an important life function?  The Cell Cycle All cells follow the cell cycle It is split into 4 parts: G1, S, G2, and M G1 + S + G2 phases = interphase M phase includes chromosome duplication and cytokinesis ...

Aim: How do cells reproduce? Do Now: Why is reproduction an important life function?  The Cell Cycle All cells follow the cell cycle It is split into 4 parts: G1, S, G2, and M G1 + S + G2 phases = interphase M phase includes chromosome duplication and cytokinesis The Cell Cycle Interphase (G1 + S + G2) G1: growth and synthesis ; begins after mitosis and cytokinesis ends and lasts until S phase begins G1 is the longest phase During G1, cell decides if it is going to duplicate chromosomes (go to S phase) or exit cell cycle Interphase (G1 + S + G2) S phase: chromosomes are duplicated ; each chromosome replicates exactly once to form a pair of linked sister chromatids In animal cells , pair of centrioles is also replicated Interphase (G1 + S + G2) G2: cell prepares for division From this point on, the cell enters M phase (mitosis + cytokinesis) The cell cycle can be remembered as IPMATC , where “I” is interphase , “PMAT” is mitosis, and “C” is cytokinesis  Why do cells duplicate? Allows for growth of organism ; body cells either need to increase in size or number in order for an organism to grow , division is more effective because “smaller is better” when it comes to cells The larger the cell , the harder it is for cell to maintain homeostasis Cells also divide to replace damaged and dying cells  Mitosis Occurs when a eukaryotic cell separates its chromosomes into two identical sets in two separate nuclei Followed by cytokinesis: nuclei, cytoplasm, organelles, and cell membrane are split into two separate cells  Mitosis Each new cell that is created is called a daughter cell They are genetically identical to each other and their parent (mother) cell Mitosis may result in uncontrolled cell growth (tumor or cancer) Occurs only in eukaryotic cells (cells with nucleus and cell organelles) Prokaryotic cells (no nucleus) divide by asexual reproduction  Mitosis There are four phases to mitosis: prophase, metaphase, anaphase, telophase (hint to remember: PMAT When a cell is not dividing , it is in interphase  Reasons for mitosis Development & growth: increases number of cells; allows organism to grow (zygote🡪 embryo) Cell replacement: some types of cells (skin and digestive tract) are constantly being replaced; also important in healing wounds Regeneration: some organisms can regenerate parts on their bodies (sea stars, lizards, lobsters) Asexual reproduction: some organisms produce exact copies of their offspring (hydra, sponges, planaria)  Prophase Nuclear membrane and nucleolus disappear Chromatin (DNA + proteins) condenses into chromosomes Chromosomes have been duplicated and have two sister chromatids bound at centromere Centrioles create spindle fibers that move across cell and start aligning themselves with kinetochores on chromosomes  Metaphase Spindle fibers attach to chromatids and line up the chromatids along metaphase plate (like an equator in middle of cell) This organization is necessary so that when chromosomes separate (in next phase) one set of chromosomes goes to each new cell  Anaphase Sister chromatids split and become separate daughter chromosomes Spindle fibers start pulling chromosomes towards opposite ends of the cell  Telophase Spindle fibers continue pulling chromosomes towards opposite ends of cell Nuclear membranes form around both sets of chromosomes and chromosomes become less condensed Mitosis is now complete! Cytokinesis: End of the Cell Cycle Cleavage furrow forms (in animal cells) and pinches off two separate cells In plant cells, a cell plate forms which becomes new cell walls for two new cells  Mitosis in Plant Cells There is a preprophase stage in which a sheet of cytoplasm (phragmosome) bisects the cell where cell division will occur Centrioles are not present Cytokinesis occurs by formation of cell plate  Summary The cell cycle is made up of four phases: G1, S, G2, and M Interphase describes the time when the cell is not dividing Mitosis is a series of phases in which chromosomes replicate and then separate Mitosis is important for growth and repair of organisms Cytokinesis occurs when cell separates into two new cells