mitosis/meiosis
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Mitosis/Meiosis. Cell Growth. Reason: Large cells create more of a demand on DNA Trouble moving enough nutrients and wastes across cell membrane. Importance: cells regenerate Repair/renew Growth reproduction. Reproduction Asexual 1 parent - PowerPoint PPT PresentationTRANSCRIPT
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Mitosis/Meiosis
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Cell Growth
• Reason: – Large cells create more of a demand on DNA– Trouble moving enough nutrients and wastes
across cell membrane
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• Importance: cells regenerate– Repair/renew– Growth– reproduction
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• Reproduction– Asexual • 1 parent• Simple cell division- cells duplicate genetic material,
splits into 2 new identical offspring– Ex: Paramecium, sea stars
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• Sexual Reproduction– 2 parents– Genetic material combine- offspring differ from
parents– Union of sex cells (egg + sperm)
• Ex: multicellular organisms, single celled organisms
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• 2 types of cell division– Mitosis– Meiosis
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Cell Cycle
• Chromatin- fibers containing protein + DNA• Chromosomes- chromatin condensed into
visible structures - thousands of genes
• Ex: Humans= 46 chromosomes
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• Before cell division- chromosomes duplicate• Sister chromatids- identical copies joined• Centromere- joins chromatids
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Cell Cycle• Birth of cell till time it reproduces• Interphase (90%)– G1 (gap)– S phase (synthesis)– G2
• M Phase (mitotic)• Cytokinesis
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• Cytokinesis- cytoplasm divides– (1 nucleus, cytoplasm, plasma membrane)
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Cytokinesis in Animal Cells
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Cytokinesis in a Plant Cell
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Mitosis• http://www.youtube.com/watch?v=2WwIKdy
BN_s&feature=related• Spindle- microtubules that guide movement of
chromosomes• Centrosomes- spindles grow from here– Contain centrioles in animal cells
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Draw stages of mitosis
• Pg 246-247• Draw each stage of mitosis, the drawing should be
neat and in color• Label each phase and include a detailed description
of what is occurring in each• Label– Centrioles - spindle– Chromatin - centromere– Chromosomes - sister chromatids– Nuclear envelope
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Prophase• chromatin condenses into
chromosomes• Nuclear envelope breaks
down• Mitotic spindle forms • Centrioles move to opposite
sides of the cell
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Metaphase• Chromosomes line up
across center of cell• Chromosomes attached to
spindle fibers by centrioles
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Anaphase• Sister chromatids separate• Move toward poles by
spindles, microtubules shorten
• Microtubules also lengthen and push poles apart
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Telophase• Chromosomes reach poles
of spindle• Spindles disappear• 2 nuclear envelopes reform• Chromosomes uncoil and
lengthen
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Mitosis in a Whitefish
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Mitosis in Animal Cells
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Mitosis in a Plant Cell
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Tumors and Cancer
• Out of control cell reproduction = mass of cells or tumor
• Benign Tumor– Removable by surgery– Cells remain at original site
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• Malignant Tumor- masses of cells from reproduction of cancer cells
• Cancer- disruption of cell cycle• Metastasis- spread of cancer cells beyond
original site
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Cancer Treatment
• Removed by surgery• Radiation therapy- high energy radiation
disrupts cell division• Chemotherapy- drugs which disrupts cell
division
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Meiosis
• Cell division= 4 cells each– ½ the number of chromosomes as parent
• Occurs in sex organs
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• Karyotypes- display of chromosomes– Each with twin that resembles size + shape– Inherit one chromosome of each pair from mother
and father= Homologous chromosome
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Homologous Chromosome
• same sequence of genes• Control same inherited characteristics• Ex: eye color gene located on same place of
the homologous chromosomes but one gene may call for blue the other brown
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• Humans- 23 homologous chromosomes– Females– Males
• Sex chromosomes – Male XY– Female XX
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• Diploid (2n)- 2 homologous sets of chromosomes
• Haploid (n)- single set of chromosomes, produced by meiosis
n = 23 2n =46 2(23)=46
Fertilization- haploid cells fuse (egg + sperm)Zygote- fertilized egg - diploid
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• Spermatogenesis- making sperm cell – all four cells develop into sperm
• Oogenesis –making an egg cell=one egg
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Process of Meiosis
• Life cycles of all sexual reproducing organisms alter haploid and diploid stages
• Keeps chromosome # from doubling every generation
• Exchange of genetic material b/w homologous chromosomes
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• 2 meiotic division– Meiosis I- homologous
chromosomes separated– Meiosis II- sister
chromatids are separated into haploid cells
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Prophase I• HC stick together = 4
chromatids (tetrad)• Spindle attaches to tetrad• Crossing over- sister
chromatids exchange material
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Metaphase I• tetrads move to middle of
cell and line up
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Anaphase I• HC separate and move to
opposite ends
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Telophase I and Cytokinesis• Chromosomes arrive at
opposite poles• Nuclear envelope begins
to form• Cytokineses occurs
forming 2 haploid cells
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Prophase II• spindle forms and attaches
to centromeres
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Metaphase II• chromosomes line up in
center
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Anaphase II• sister chromatids separate
and move to opposite poles
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Telophase II and Cytokinesis• Chromatids considered
individual chromosomes arrive at opposite poles
• Cytokinesis splits cells• Produce 4 haploid daughter
cells
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Genetic Variation
• Assortment of chromosomes- happens by chance
• Formula for different combinations- 2ⁿ Ex: Humans 2²³ = 8 million possible combos
• Crossing Over- exchange of genetic material between homologous chromosomes– Occurs during prophase– Genetic recombination
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