Cell dIVISION

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Cell dIVISION

• Mitosis and Meiosis
• Asexual v. Sexual Reproduction

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Cell Division

• process where 1 cell splits into 2
• Replaces somatic (body) cells in multicellular
  organisms
• Allows for multicelullar growth
• Allows for asexual reproduction in plants

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• Chromosome rod shaped structure made up
• DNA and protein
• a. held together by centromere
• - holds chromatids together until they
• separate during division
• b. only found during cell division

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Chromosome Number

• Human/animal chromosomes sex chromosomes
  and autosomes
• Humans have 46 chromosomes in somatic cells
• Karyotype used to examine an individuals
  chromosomes

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Haploid Diploid
Reproductive cells (sperm and egg) Somatic cells (body-all other cells)
½ the of chromosomes (23) Has ALL chromosomes (46)
half the DNA Has ALL DNA
N haploid 2N diploid
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Haploid/Diploid Problems

• Haploid ? Diploid sex cell ? body cell ( x by
  2)
• Diploid ? Haploid body cell ? sex cell ( by
  2)
• Diploid ? Diploid body cell ? body cell
  Haploid ? Haploid sex cell ? sex cell

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Practice Problems

• Dogs have 42 chromosomes in their diploid cells.
  How many are in their haploid cells?
• If there are 23 chromosomes in a sperm cell, how
  many would be in the skin cell?
• If there are 46 chromosomes in a nerve cell, how
  many would be in a blood cell?
• If there are 23 chromosomes in a sperm cell, how
  many would be in a human ovum (egg)

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Cell Division in Prokaryotes

• Binary Fision two identical cells are produced
  from one cell
• division in bacteria

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Cell Division in Eukaryotes
Mitosis Meiosis
Asexual Reproduction Sexual Reproduction
Division of diploid cells (somatic cells) Division of haploid cells (reproductive cells)
Results in 2 identical daughter cells Results in 4 haploid daughter cells
1 division 2 divisions
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Cell Cycle

• series of events leading to cell division

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Mitosis

• Asexual Reproduction
• Diploid cells split into 2 identical diploid
  cells
• Allows body cells to be replaced and cells to GROW

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Phases of Mitosis

• 1. Prophase

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• 2. Metaphase

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• 3. Anaphase

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• 4. Telophase

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Cytokinesis
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Meiosis

• sexual reproduction
• Fusing of 2 haploid gametes to form 1 diploid
  zygote

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Stages

• 2 divisions
• a. Meiosis I

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• b. Meiosis II

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Sources of Genetic Variation

• Crossing over
• Fertilization
• Independent Assortment