Meiosis Notes

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Meiosis Notes
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KEY CONCEPT Gametes have half the number of
chromosomes that body cells have.
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• 2 Types of Cells
• Body cells are also called somatic cells.
• Gametes are also called Sex Cells
• Egg (Female)
• Sperm (Male)

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• Human somatic cells have 23 pairs of chromosomes.
• Homologous pairs of chromosomes have the same
  structure.
• For each homologous pair, one chromosome comes
  from each parent.
• Chromosome pairs 1-22 are autosomes.
• Sex chromosomes, X and Y, determine gender in
  mammals.

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• Diploid (2n) cells have two copies of every
  chromosome.

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• Haploid (n) cells have one copy of every
  chromosome.

• Gametes are haploid.
• Gametes have 22 autosomes and 1 sex chromosome.

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• Meiosis makes haploid cells from diploid cells.

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• Meiosis reduces chromosome number by ½ and
  creates genetic diversity.

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homologous chromosomes
One chromosome of this matched pair is a homolog.
sister chromatids
sister chromatids
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• Sperm primarily contribute DNA to an embryo.

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• Eggs contribute DNA, cytoplasm, and organelles to
  an embryo.
• During meiosis, the ONE egg gets most of the
  contents the other cells form polar bodies.