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Chapter 4.3: MEIOSIS Life Science
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Meiosis (my Oh sus) Meiosis – a part of sexual reproduction in which cells divide to form sperm cells in a male and egg cells in a female.
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MEIOSIS I and II 1. Meiosis I – cells divide to produce two duplicate cells of 46 chromosomes. 2. Meiosis II- cells produced in Meiosis I divide to produce four cells with half the number of chromosomes= 23 chromosomes (in humans)
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Look at the Cells during Meiosis…
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Number of Cells Produced
Mitosis Meiosis Type of Reproduction Type of Cell Produced Number of Cells Produced Number of Chromosomes
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Recap… Asexual Reproduction – organism produced from ????? parent cell
Like Bacteria!!! Sexual Reproduction – organism produced from ????? parent cells Organism inherits traits from BOTH parents Like You!!!
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Sexual Reproduction Sexual Reproduction- when 2 sex cells, usually an egg and sperm, come together. Each sex cell contributes half the chromosomes… ***Half From MOM & Half from DAD!
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NEW VOCAB Fertilization- is the joining of an egg and a sperm, from two different organisms. a. A Cell that forms from fertilization is called a Zygote.
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NOT A ZEBRAGOAT!
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GAMETES Gametes = SEX CELLS = Reproductive Cells
1. Egg- formed in Female reproductive organs 2. Sperm- formed in Male reproductive organs
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CHAPTER HOME Image Gallery BACK TO IMAGE GALLERY
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Human Diploid Cell Body cells are Diploid because they contain 23 pairs of chromosomes!
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Human Haploid Cell Sex cells are a little different…
Sex Cells are Haploid because they contain 23 single chromosomes!
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Meiosis
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MEIOSIS FLIP BOOK
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Meiosis I Interphase I- Prophase I-
Chromatin is doubling & spreading out Centrioles are doubling Nucleus is growing Prophase I- Chromosomes double and pair 2 by 2 Nucleus disappears Spindle Fibers appear Centrioles move to opposite sides
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Meiosis I Metaphase I- Anaphase I-
Chromosomes line up in MIDDLE 2 by 2 Spindle fibers attach to centromeres Anaphase I- Chromosomes move to centrioles 1 whole chromosome moves one way- other moves other way
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Meiosis I Telophase I- The cell cuts in half Spindle Fibers disappear
Nucleus Appears 2 cells are formed (46 chromosomes each)
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Meiosis II The 2 new cells divide again Repeats the 4 stages
Total of 4 sex cells are created, each with half the number of chromosomes Page 109
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Meiosis II Intermission- Cell takes a break… Prophase II-
Spindle Fibers appear Nucleus disappears Centrioles double and move to opposite ends
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Meiosis II Metaphase II- Anaphase II-
Chromosomes line up in middle of cell Spindle fibers attach to centrioles and centromeres Anaphase II- Half of chromsomes (chromatids) move to opposite ends
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Meiosis II Telophase II- Yay we are finished our flip book!!!
Nucleus appears 4 Total Cells – (23 chromatids in each one) Each cell has ½ the number of the original Yay we are finished our flip book!!!
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