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MITOSIS
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Mitosis and Meiosis Mitosis: -division of somatic (body) cells Meiosis
-division of gametes (sex cells)
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Mitosis: Meiosis: Explain the randomness in meiosis End of first class
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Mitosis: If a cell wants to make a duplicate of itself, it first must copy its DNA (part of a chromosome). The copies then must be separated & sorted into two sides of the cell. The cell then splits in two. Part of each parent is carried to the two new cells. Results in cells such as internal organs, skin, bones, blood, etc.
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To Be Answered… THINK: * How many cells are you composed of?
* When an organism grows bigger do you get more cells or just bigger cells or both? * When do your cells divide the fastest? Slowest? * Do cells ever stop dividing? * Are all cells capable of division and replacement? Thanks to person who introduced me Explain presentation style Different, wacky, interactive Reason for madness- will be reviewed during implications May be asked to be an active participant May be asked to reinforce others Will be reinforced with candy Comments/questions welcomed throughout Reinforce me for doing well Have participants guess the number of new things they will learn today
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Why Would a Cell Divide? Solution: divide in 2!
As cells absorb nutrients and get larger, the volume of the cell increases faster than the surface area This means that a cell can no longer absorb nutrients and get rid of wastes fast enough to support its demands (volume) So what’s a cell to do? Solution: divide in 2! Surface area for exchange not great enough to support cell’s needs Thanks to person who introduced me Explain presentation style Different, wacky, interactive Reason for madness- will be reviewed during implications May be asked to be an active participant May be asked to reinforce others Will be reinforced with candy Comments/questions welcomed throughout Reinforce me for doing well Have participants guess the number of new things they will learn today
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When Would a Cell Divide?
Growth Repair or Replacement Cancer Different cells divide at different rates: Most mammalian cells = hours Some bacterial cells = minutes Thanks to person who introduced me Explain presentation style Different, wacky, interactive Reason for madness- will be reviewed during implications May be asked to be an active participant May be asked to reinforce others Will be reinforced with candy Comments/questions welcomed throughout Reinforce me for doing well Have participants guess the number of new things they will learn today
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Getting Older… How does cell division change over a lifetime?
All cells are only allowed to complete a certain number of divisions Then they die (programmed cell death) How does cell division change over a lifetime? Childhood cell division > cell death Adulthood cell division = cell death The Later Years cell division < cell death Thanks to person who introduced me Explain presentation style Different, wacky, interactive Reason for madness- will be reviewed during implications May be asked to be an active participant May be asked to reinforce others Will be reinforced with candy Comments/questions welcomed throughout Reinforce me for doing well Have participants guess the number of new things they will learn today
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During Interphase DNA replicates which must occur before Mitosis can begin .
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10X Magnification of Stained Human Cheek Cells
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Parts of the Human Cheek Cell at 40X Magnification
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Can you name these parts of the Human Cheek Cell?
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CELL CYCLE
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Mitosis Interphase Interesting things happen!
Cell preparing to divide Genetic material doubles Animal cell Plant cell
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Interphase occurs just before Mitosis begins:
DNA is replicated along with organelles and other cellular components and the cell prepares for division.
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Mitosis Prophase Chromosome pair up! Chromosomes thicken and shorten
-become visible -2 chromatids joined by a centromere Centrioles move to the opposite sides of the nucleus Nucleolus disappears Nuclear membrane disintegrate Animal cell Plant cell
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Mitosis Metaphase Chromosomes meet in the middle!
Chromosomes arrange at equator of cell Become attached to spindle fibres by centromeres Homologous chromosomes do not associate Animal cell Plant cell
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Mitosis Anaphase Chromosomes get pulled apart.
Spindle fibres contract pulling sister chromatids to the opposite poles of the cell Animal cell Plant cell
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Mitosis Telophase Now there are two! Chromosomes uncoil
Spindle fibres disintegrate Centrioles replicate Nuclear membrane forms Cell divides Animal cell Plant cell
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After Mitosis: Cytokinesis
Beginning of cytokinesis in a plant: The actual splitting of the daughter cells into two separate cells is called cytokinesis and occurs differently in both plant and animal Cells. Beginning of cytokinesis in an animal:
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View of onion root tip under low power
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MITOSIS – ONION ROOT TIP
Interphase Prophase Later Prophase Metaphase Early Anaphase Anaphase Telophase Later Telophase
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STAGES OF MITOSIS IN WHITEFISH BLASTULA
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Review of the stages!
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Interphase This cell is shown, as this is how all cells look before mitosis. Please be aware that Interphase is a phase of the cell cycle, but NOT a stage of mitosis.
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Mitosis - Early Prophase
To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).
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Mitosis - Metaphase The spindle has now formed and the nuclear membrane has broken down. The chromosomes are lined up along the cell's center and are attached to the spindle fibers. When the individual chromatids (½ of the "X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome (i.e. In metaphase, the chromosome, composed of two chromatids, separates into the individual chromatids, which are then renamed chromosomes).
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Mitosis - Anaphase The newly formed chromosomes are pulled along the spindle toward opposite poles of the cell.
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Mitosis - Telophase The chromosomes have finished their migration to the poles. The spindle has broken down and disappeared. The cell membrane pinches in (forms a cleavage furrow) along the center creating two separate cells . At this time, the chromosomes uncoil and become less visible (as they are during Interphase), the nuclear membrane reforms. The division of the cytoplasm is called cytokinesis. The division of the nucleus is Mitosis. At the end of Telophase, the cell reenters Interphase.
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The X is pointing to what structure?
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Put the stages in the correct order.
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Mitosis Mitosis animations:
Beginning of second class
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Meiosis Meiosis animation:
Beginning of third class
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