Agenda

1
Agenda
Why is it important that meiosis produces haploid
cells? What is a tetrad? What stage of meiosis
can crossing over occur in? Why is crossing over
important?

• Go over Vocabulary set 2 Definitions
• Go over Section 8-2 Review Worksheet
• Notes Meiosis
• Complete Meiosis Skill Worksheet

2

• Binary fission- a form of asexual reproduction in
  prokaryotes
• Mitosis- process of cell division that forms two
  new nuclei each with the same number of
  chromosomes
• Asexual reproduction- reproduction that does not
  involve the union of gametes offspring are
  genetically identical to parent
• Meiosis- process of cell division during which
  the number of chromosomes decreases to half the
  original number by two divisions of the nucleus
• Gamete- reproductive cell sperm or egg
• Cell plate- the precursor of a new plant cell
  wall that forms during cell division
• Cytokinesis- division of cytoplasm
• Spindle fiber-one of the microtubules that assist
  in the movement of chromosomes in dividing
  eukaryotic cells
• Synapsis- pairing of homologous chromosomes
  during meiosis
• Tetrad- four chromatids in a pair of homologous
  chromosomes that come together as a result of
  synapsis
• Crossing-over- the exchange of genetic material
  between homologous chromosomes during meiosis
  that results in genetic diversity
• Genetic recombination- regrouping of genes in
  offspring that results in a genetic makeup
  different than parents
• Independent assortment- random distribution of
  the genes to gametes
• Spermatogenesis- the process by which male
  gametes form
• Oogenesis- the process by which female gametes
  form
• Polar body-a short lived product of the formation
  of gametes by meiosis
• Sexual reproduction- reproduction in which
  gametes fuse

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Meiosis
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Sexual reproduction requires meiosis.

• Meiosis produces haploid (n) gametes so that
  after fertilization, the embryos will be diploid.
• Meiosis also permits recombination (crossing
  over) so that each new gamete will have genes
  from both mother and father.

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Prophase I
Metaphase I
Anaphase I
Telophase I
Homologous chromosomes synapse or pair. (tetrad)
Crossing over occurs. Spindle fibers form.
Microtubule spindle apparatus attaches to
chromosomes. Homologous pairs align along spindle
equator.
Homologous pairs of chromosomes separate and move
to opposite poles.
One set of paired chromosomes arrives at each
pole, and nuclear division begins.
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Prophase II
Metaphase II
Anaphase II
Telophase II
Chromosomes recondense. Spindle fibers form
between centrioles (if present).
Microtubule spindle apparatus attaches to
chromosomes. Chromosomes align along spindle.
Sister chromatids separate and move to opposite
poles.
Chromatids arrive at each pole, and cell division
begins.
4 haploid daughter cell. Genetically different
due to independent assortment.
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Crossing-over happens in early prophase I of
meiosis.
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Crossing Over
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Why is recombination important?
Biodiversity
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Review

• Why is it important that meiosis produces haploid
  cells?
• What is a tetrad?
• What stage of meiosis can crossing over occur in?
• Why is crossing over important?

12
Agenda
How is spermatogenesis different than
oogenesis? What is a polar body?

• Vocabulary Review Game
• Notes
• Read Lecture Four Sexual Evolution From X to Y
• Web Activity
• Complete Essay

Dont forget Vocabulary Set 2 Quiz is Wednesday!
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Spermatogenesis- Production of sperm cells

• Produces four haploid sperm cells

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Oogenesis- Production of mature egg cells
or ova

• Produces one haploid egg cell and 3 polar bodies
  which degenerate

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Mitosis Meiosis comparison
Recombination happens here
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Mitosis Meiosis comparison II.
(mitosis ends here)
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ReviewHow is spermatogenesis different than
oogenesis?What is a polar body?

• Read Lecture Four Sexual Evolution From X to Y
• Web ActivityLog onto Howard Hughs Medical
  Institute Website and select Gender Testing for
  Female Athletes
• http//www.hhmi.org/biointeractive/gender/index.ht
  ml
• Complete Essay