Chapter 13 Meiosis and Sexual Life Cycles

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Chapter 13 Meiosis and Sexual Life Cycles
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Question?

• Does Like really beget Like?
• The offspring will resemble the parents, but
  they may not be exactly like them.

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Heredity
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Genetics
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Genes
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Reproduction
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Asexual Reproduction
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Asexual Bud
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Advantages
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Disadvantages
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Sexual Reproduction
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Advantages
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Disadvantages
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Question ?

• Do parents give their whole DNA copy to each
  offspring?

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Chromosome Number
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Life Cycle - if Mitosis

• Female 46 Male 46
• egg 46 sperm 46
• Zygote 92
• mitosis
  mitosis

Mitosis
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Result
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Life Cycle - if Meiosis

• Female 46 Male 46
• egg 23 sperm 23
• Zygote 46
• mitosis
  mitosis

Meiosis
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Result
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Meiosis - Purpose
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Sexual Life Cycle
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(No Transcript)
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Ploidy
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Diploid
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(No Transcript)
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(No Transcript)
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Haploid
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Polyploids
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Life Cycle Variations
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Meiosis/Mitosis Preview of differences
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Meiosis/Mitosis Preview of differences
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Meiosis
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LE 13-9
MITOSIS
MEIOSIS
Chiasma (site of crossing over)
Parent cell (before chromosome replication)
MEIOSIS I
Propase
Prophase I
Chromosome replication
Chromosome replication
Tetrad formed by synapsis of homologous chromosome
s
Duplicated chromosome (two sister chromatids)
2n 6
Tetrads positioned at the metaphase plate
Chromosomes positioned at the metaphase plate
Metaphase I
Metaphase
Anaphase
Sister chromatids separate during anaphase
Anaphase I
Homologues separate during anaphase
I sister chromatids remain together
Telophase
Telophase I
Haploid n 3
Daughter cells of meiosis I
2n
2n
MEIOSIS II
Daughter cells of mitosis
n
n
n
n
Daughter cells of meiosis II
Sister chromatids separate during anaphase II
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Prophase I
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Prophase I
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Metaphase I
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Anaphase I

• .

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Anaphase I
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Telophase I
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Interkinesis
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Meiosis II
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Meiosis - Results
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Sexual Sources of Genetic Variation

• 1.

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Independent Assortment
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Gamete Possibilities
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Random Fertilization
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Random Fertilization
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Result

• Is it any wonder that two offspring from the same
  human parents only resemble each other and are
  not identical twins?

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Crossing-Over
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Chiasmata
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(No Transcript)
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Importance
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Importance
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Comments
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Comments
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Summary

• Know how the chromosomes separate during Meiosis.
• Know how Meiosis differs from Mitosis.
• Know how sexual reproduction increases genetic
  variation.