Sexual and Asexual Reproduction

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Sexual and Asexual Reproduction

• Meiosis and Mitosis

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What is the differencebetween the hydras
offspring growing off of the parent hydra and
the two beetles mating to create their offspring?
How could a cell make an exact copy of itself?
Engage/pH 0708
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Exploring the Cell Cycle

• Directions
• There are six stations of microscopes around
  the classroom. Each slide shows a cell (indicated
  by the pointer) in a different phase of mitosis.
  At each station determine which stage the cell is
  in using the diagram of mitosis.

Explore/pH 0708
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Remember chromosomes?
Explain/pH 0708
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Exploring Mitosis
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Mitosis

• Cell Division Cell copying
• Creates new cells with identical DNA
• If a human cell goes through mitosis, it starts
  with 46 chromosomes and ends up with 46
  chromosomes in the new cell.
• These cells are called 2n they have two copies
  of each chromosome
• Dipliod

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(No Transcript)
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Interphase
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Stages of Mitosis

• Prophase

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Metaphase
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Anaphase
Centrioles at each pole have fibers called
microfilaments that pull chromosomes apart at the
centromere.
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Telophase
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Cytokinesis
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Video of Mitosis

• Mitosis Video

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The Cell Cycle
If a cell gets stuck in the cell cycle and
divides uncontrollably, a tumor (mass of cells)
will form. The cell is a cancer cell. Cancer
cells lose the ability to regulate mitosis and do
not recognize the signs to stop dividing
(Contact Inhibition).
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SOME TUMORS
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MRI of Brain Tumor
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Meiosis

• Meiosis creates gametes (sperm and egg cells)
• Sperm and Egg Cells have HALF the number of
  chromosomes as body cells
• In a human sperm or egg cell there are 23
  chromosomes
• We call these 1n because they have only one copy
  of each chromosome, they are haploid

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Comparing Mitosis and Meiosis
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Errors in Meiosis

• If an error occurs during Meiosis, you could end
  up with more or less chromosomes in the
  egg/sperm.
• This is called nondisjunction
• Disorders that could happen because of this are
  Trisomy 21 (Downs Syndrome)
• Disorders

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How does this relate to the Karyotypes you made?
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Lets compare Mitosis and Meiosis

• Mitosis vs. Meiosis
• Mitosis and Meiosis

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Asexual Reproduction

• One individual organism creates offspring that
  are genetically identical to itself.
• This occurs through MITOSIS.
• Sea stars, Sea anemones, hydra, some plants

Hydra Budding
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Sexual Reproduction

• Two gametes (sperm and egg) come together to form
  a new organism
• One set of chromosomes (1n) comes from the
  mothers egg
• One set of chromosomes (1n) comes from the
  fathers sperm
• When these join a new organism that is 2n (has
  two copies of each chromosome) forms

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Is this new organism an exact copy of the parent?

• NO!

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Why is sexual reproduction important?

• Sexual reproduction increases the genetic
  diversity of a species of organisms
• Beneficial mutations can accumulate faster in a
  species
• This can help the species adapt and survive over
  time