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Quick review: identify this stage of the diploid cell cycle. Prophase. Quick review: identify this stage of the diploid cell cycle. telophase. Quick review: identify this stage of the diploid cell cycle. anaphase. Quick review: identify this stage of the diploid cell cycle. Prophase.

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Presentation Transcript
slide8

Meiosis

  • Defined: Process where the chromosome number is reduced by half
  • Gametes created (egg, sperm, pollen)
  • End Result: Four Haploid Cells
slide9

Interphase

  • Same process
    • G1: Growth, organelle replication, normal functions
    • S: Chromatin duplicated
    • G2: Growth and normal functions
synthesis s stage
Synthesis (S stage)

Chromatin duplicated

slide11

Prophase 1

Mom 1

  • Similar to mitosis, except…
  • Two Events:
    • 1) Synapsis: Pairing of homologous chromosomes
        • Dad’s #1 chromosome pairs with Mom’s #1, etc…
        • The four paired chromatids equals a TETRAD
    • 2) Crossing Over: Exchange of genes

Dad 1

early prophase
Early Prophase

2

Chromosomes form

1

3

2

Nucleus dissolves

3

1

synapsis
Synapsis

tetrad

tetrad

2

Spindle fibers pull homologous chromosomes together

1

3

2

3

1

tetrad

slide14

Metaphase 1

  • Homologous chromosomes (tetrads) align along cell equator

2

2

1

1

3

3

slide15

Anaphase 1

  • Homologous chromosomes are pulled apart
    • Tetrads separated

1

1

3

3

2

2

slide16

Telophase 1

  • Cytokinesis divides the cells
    • Not apart of telophase
  • Each cell contains 1 of the homologous chromosomes
    • In humans = 23 chromosomes

1

1

3

3

2

2

prophase 1
Prophase 1

2

Chromosomes form

1

3

2

Nucleus dissolves

3

1

prophase 1 synapsis
Prophase 1 (Synapsis)

tetrad

tetrad

2

Spindle fibers pull homologous chromosomes together

1

3

2

3

1

tetrad

slide20

Metaphase 1

2

2

1

1

3

3

Tetrads pulled to middle of cell

slide21

Anaphase 1

1

1

3

3

2

2

Tetrads pulled apart… one entire chromosome to each end of the cell

telophase 1
Telophase 1

1

1

3

3

2

2

Nucleus reforms… Cell Plate forms

Cytokinesissplits the cell into two…

slide23

Prophase 2

  • Same as mitosis
  • Note: No new DNA was created (no 2nd interphase)

1

1

3

3

2

2

slide24

Metaphase 2

  • Remaining chromosomes are aligned at cell equator

1

1

3

3

2

2

slide25

Anaphase 2

  • Chromatids are pulled to opposite ends
slide26

Telophase 2

  • Nucleus reforms on the four new cells
  • Cell plate forms
  • Cytokinesis divides the cells
    • Not apart of telophase
  • Chromatids uncoil
  • End Result: Four haploid cells
slide27

Spermatogonium

(diploid)

Spermatogenesis

Meiosis 1

  • Defined: Production of sperm cells
  • Location: male testes
  • Makes final changes to sperm cell
  • Four haploid sperm cells at a time

Meiosis 2

Spermatogenesis

slide28

Oocyte

(diploid)

Oogenesis

Meiosis 1

  • Defined: Production of the egg cell (ovum)
  • Location: female ovaries
  • During meiosis I: Cytoplasm distributed unequally
  • During meiosis II:cells split again
  • End result: 1 mature cell, 3 polar bodies

Meiosis 2

Oogenesis

slide29
Division of somatic cells

Ex: Blood cells, skin cells, nerve cells…

End Result: 2 Diploid Cells

Importance: Replaces aging cells

Importance: Form of asexual reproduction

Division of gametes

Ex: Sperm and Egg cells

End Result: 4 Haploid cells

Importance: Reduces the gamete chromosome number by half

Mitosis

Meiosis

prophase 11
Prophase 1

2

Chromosomes form

1

3

2

Nucleus dissolves

3

1

prophase 1 synapsis1
Prophase 1 (Synapsis)

tetrad

tetrad

2

Spindle fibers pull homologous chromosomes together

1

3

2

3

1

tetrad

slide33

Metaphase 1

2

2

1

1

3

3

Tetrads pulled to middle of cell

slide34

Anaphase 1

1

1

3

3

2

2

Tetrads pulled apart… one entire chromosome to each end of the cell

telophase 11
Telophase 1

1

1

3

3

2

2

Cytokinesis splits the cell into two…

Nucleus reforms

prophase 2
Prophase 2

1

1

3

3

2

2

Nucleus dissolves….

Spindle fibers form

metaphase 2
Metaphase 2

1

1

3

3

2

2

Chromosomes are pulled to middle of each cell

anaphase 2
Anaphase 2

Chromosomes split apart…

One chromatid pulled to each end of the cell

telophase 2
Telophase 2

Nucleus reforms… cell plate created

Cytokinesissplits the two cells into four cells…

Chromatidsunwind into chromatin

review
REVIEW

1) Name three ways that meiosis and mitosis differ.

2) Pick a stage of meiosis…any stage. Describe what happens in it.

3) What type of cells does meiosis create?

4) What are homologous chromosomes?

5) When do homologous chromosomes move to opposite ends of the cell?

6) When do chromatids move to opposite ends of the cell?

7) Why is no DNA created in meiosis 2?

8) How does meiosis differ in males vs. females?