Reviewing%20Mitosis

1
Reviewing Mitosis

• Comparing Plant Animal Cells

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Animal vs. Plant Mitosis

• Animal Cells
• Have centrioles!
• Cytokinesis simple pinching of cell membranes

• Plant Cells
• No centrioles
• Equatorial plate
• Cytokinesis must form 2 membranes PLUS 2 cell
  walls

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Meiosis

• Formation of Gametes

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Definitions

• Gamete
• Sperm
• Ovum (plural ova)
• Testes
• Ovaries
• Zygote
• Fertilization
• Haploid
• Diploid

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Meiosis

• Two nuclear divisions
• Creates haploid gametes
• In animals, sperm and ova
• In plants, spores
• Crossing Over occurs
• 4 daughter cells are created.

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Crossing-Over
Section 11-4
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Meiosis Leads to Genetic Recombination!!!
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Meiosis I Separation of Homologues

• Prophase I
• Chromosomes Condense
• Nuclear Envelope Disappears
• Spindle Formed (Asters seen here)
• Homologues Pair Up
• Crossing-over occurs here!

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Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Metaphase I

• Homologous chromosomes move to equator

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Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Anaphase I

• Homologues separate
• Chromatids do not separate from centromeres!

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Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Telophase I

• Nuclear envelope usually does not reform.
• Chromosome number in 2 new cells is now half
  because chromatids did not separate.
• THIS IS REDUCTION DIVISION!
• Cytokinesis may or may not occur.

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Figure 11-15 Meiosis
Section 11-4
Meiosis I
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Meiosis II

• No replication of chromosomes!!!!
• Proceeds just like mitosis
• Starts and ends with haploid cells

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Figure 11-17 Meiosis II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter
cells, each with half the number of chromosomes
as the original.
The chromosomes line up in a similar way to the
metaphase stage of mitosis.
The sister chromatids separate and move toward
opposite ends of the cell.
Meiosis II results in four haploid (N) daughter
cells.
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Ovum Formation

• Meiotic stages are the same
• One daughter cell keeps ALL of the cytoplasm
• Other 3 daughter cells only have genetic material
  Polar Bodies (Barr Bodies)

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Sperm Formation

• Cytoplasm and Nuclear Material Divides evenly.
• Flagella are added last to the cells following
  differentiation
• Define differentiation in your notes here.

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Fertilization

• The haploid sperm and egg fuse to create a
  diploid zygote.