LE22­Meiosis
Body Cells
vs. Sex Cells:
Body Cells (somatic) Examples:
# of chromosomes:
Type of cell division: Sex Cells (gametes) Examples:
# of chromosomes:
Type of cell division:
LE22­Meiosis
*Review:
Prophase
• replicated chromosomes are visible
• centrioles begin to move to
opposite poles
• spindle fiber begins to form
Metaphase
• sister chromatids line up at the center of the
cell
• sister chromatids separate from each
other
Anaphase
• each chromatid reaches the "poles"
of the cell
Telephase
• new nuclear membrane
forms
*Label each phase and describe what is happening.
*Is this an animal cell or plant cell? How can you tell? What would the difference be?
LE22­Meiosis
Mitosis
http://www.cellsalive.com/mitosis.htm
Why is DNA replicated only once before meiosis even though there are two rounds of cell division?
2N
(23 pairs)
DNA Replication
4N
(23 tetradsdouble pairs)
Meiosis I (1st cell division)
2N
(23 pairs)
2N
(23 pairs)
Meiosis II (2nd cell division)
N
(23)
N
(23)
N
(23)
N
(23)
LE22­Meiosis
Meiosis in Gonad (sex organ)
Homologous Chromosomes
2n
Sister Chromatids
Replicated
Homologous Chromosomes
Centromere
Tetrad
Crossing
Over
1st Meiotic Division
Disjunction
of Homologous Chromosomes
2nd Meiotic Division
Gametes
LE22­Meiosis
Meiosis
http://www.cellsalive.com/meiosis.htm
LE22­Meiosis
What is Meiosis?
haploid
diploid
haploid, reproductive cells: sperm and egg (gametes)
2
Reproductive organs
Spermatogenesis (testes)
­ making sperm
2n(diploid)
4 n(monoploid/haploid) cells
46
46
23
46
23 23
23
LE22­Meiosis
Oogenesis (ovaries)
­ making egg cells
4 n (monoploid/haploid) cells*
2n (diploid)
(only 1 egg)
46
46
23
46
23
23
23
Polar bodies (disintegrate)
Egg (ovum)
Create a venn diagram on the back of your sheet to compare mitosis and meiosis.
LE22­Meiosis
LE22­Meiosis
LE22­Meiosis
Question Sheet
LE22­Meiosis
LE22­Meiosis
LE22­Meiosis
LE22­Meiosis
LE22­Meiosis