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Cell Growth & Division: Meiosis
Chapter 11 Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
I. Meiosis Nuclear division that produces sex cells /gametes In REPRODUCTIVE ORGANS only 2 divisions: Meiosis I & Meiosis II Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
II. Stages PROPHASE I 1. centrioles & spindle fibers appear 2. nuclear mem. & nucleolus disappear Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
3. Crossing over= exchange of genetic material between Between homologous chromosomes Ensures genetic variation! Tetrad formed Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
B. METAPHASE I 1. Chromosome PAIRS (homologous)line up in middle RANDOMLY 2. Ensures genetic variation! 3. Spindle fibers attach to centromeres Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
C. ANAPHASE I 1. Chromosome PAIRS (homologous) SEPARATE to opposite sides Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
D. TELOPHASE I 1. Nuclear membrane forms around chromosomes (temporarily). 2. Spindle fibers & centrioles disappear. 3. Cytokinesis occurs. Cell Growth & Division: Meiosis
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NO INTERPHASE!! What does that mean?
Well, there is NO DNA duplication. Cells start with 46 chromosomes before being divided again. Cell will have LESS than 46 chromosomes by the end of meiosis. Wow.
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Cell Growth & Division: Meiosis
E. PROPHASE II 1. Spindle fibers reappear. 2. Nuclear membrane disappears. 3. Starts with 46 chromosomes. Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
F. METAPHASE II 1. Chromosomes line up in middle. 2. Spindle fibers attach to centromeres. Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
G. ANAPHASE II 1. Chromosomes separate into chromatids & move to opposite ends. Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
H. TELOPHASE II 1. Spindle fibers & centrioles disappear. 2. Nuclear mem. & nucleolus reappear. 3. Cytokinesis follows. Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
I. CYTOKINESIS 1. Four non-identical cells – Back in interphase Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
III. MITOSIS VS. MEIOSIS Cell Growth & Division: Meiosis Mitosis Meiosis 2 IDENTICAL cells 4 NON-IDENTICAL cells Start =46 chr. End = 46 chr. Start =46 chr. End = 23 chr. Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
Mitosis Meiosis No crossing over Crossing over in Prophase I Makes BODY cells Makes SEX cells Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
Body Cells Sex Cells Sci. name = SOMATIC cells Sci. name = GAMETES DIPLOID HAPLOID 46 chr. (23 pairs) 23 chr. (unpaired) Cell Growth & Division: Meiosis
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IV. Miscellaneous Meiosis
Cell Growth & Division: Meiosis IV. Miscellaneous Meiosis Meiosis in males: SPERMATOGENESIS makes 4 sperm cells B. Meiosis in females: OOGENESIS makes only 1 mature egg (ovum) Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
Why only 1 egg? a. unequal division of cytoplasm in both telophase I & II Cell Growth & Division: Meiosis
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Cell Growth & Division: Meiosis
Cell Growth & Division: Meiosis
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V. Asexual & Sexual Reproduction
Cell Growth & Division: Meiosis V. Asexual & Sexual Reproduction ASEXUAL reproduction = making of offspring from 1 parent B. SEXUAL reproduction = making of offspring by combining gametes from 2 parents Cell Growth & Division: Meiosis
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