MEIOSIS NOTES (11.4)

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MEIOSIS NOTES (11.4)
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(Meiosis Notes 11.4) Reproduction

• Asexual- all of the parent DNA goes to offspring
  (miTosis-mainTains)
• Sexual -used to create sex cells(mEiosis-rEduce)

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2 TYPES OF CELLS

• BODY CELLS
• SEX CELLS

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Body Cells

• -All cells other than sex cells
• -Also called somatic cells
• -Made by mitosis
• This scanning electron micrograph (courtesy of
  Dr. Marion J. Barnhart) shows the characteristic
• biconcave shape of red blood cells.

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Body Cells

• -Contain 2 copies of each chromosome
• -homologous chromosomes
• -have diploid , 2n
• EX. Humans 46

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Sex Cells

• -Gametes
• -Eggs and sperm
• -Made by meiosis
• -Have haploid , n
• -EX. Humans 23

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How do we get 46 Chromosomes?

• Egg (haploid ) Sperm(haploid )
• ZYGOTE (diploid )
• Ex. Humans
• 23 23 46

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Meiosis ? sex cells

• mEiosis rEduction division
• -starts with 1 diploid cell and ends up with 4
  haploid cells
• Meiosis I and Meiosis II

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Meiosis I
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MEIOSIS II
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Meiosis Diagram
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CROSSING OVER

• Occurs during Prophase I of meiosis
• Tetrads form and DNA is exchanged
  XX
• ADVANTAGE genetic variation

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Crossing Over
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Egg Formation (unequal
cytokinesis)

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Comparing Mitosis and Meiosis

• HOW MANY CELLS ARE MADE?
• Mitosis
• 2
• Meiosis
• 4

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Comparing Mitosis and Meiosis

• ARE RESULTING CELLS GENETICALLY THE SAME OR
  DIFFERENT?
• Mitosis-
• Genetically the same
• Meiosis -
• Genetically different

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Comparing Mitosis and Meiosis

• WHAT TYPES OF CELLS RESULT IN THE PROCESS? (BODY
  CELLS OR GAMETES)
• Mitosis Body cells
• Meiosis Gametes

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Comparing Mitosis and Meiosis

• WHAT ARE THE ADVANTAGES OF EACH PROCESS?
• Mitosis-
• Growth and repair
• Meiosis-
• Formation of sex cells and genetic variation