Sci 103 (Spring 2006) – Outline 13
Reading:
Meiosis
P 512-515
Meiosis
1. Number of Cell divisions and Principle Events
___________ divisions occur after the chromosomes have replicated (interphase):
(a) Meiosis I – Separation of ____________________.
(b) Meiosis II – Separation of ___________________.
2. Ploidy
3. Meiosis I
(a) Prophase I:
(i) Chromosomes condense.
(ii)
(iii) Centrioles (animal cells) move to opposite poles and spindle fibers form between
them.
(iv) Nuclear envelope breaks down.
(b) Metaphase I:
(i)
(ii) Independent assortment –
(c) Anaphase I:
(d) Telophase I:
(i)
(ii) Nuclear envelope may reform (species dependent).
(e) Cytokinesis
4. Meiosis II
(a) Prophase II:
(i) Chromosomes recondense.
(ii) Centrioles move to opposite poles and spindle fibers reform.
(iii) If the nuclear envelope reformed, it breaks down.
(b) Metaphase II:
Chromosomes align at the equator of the cell and attach to the kinetochore microtubules.
(c) Anaphase II:
(d) Telophase II:
(i)
(ii) Nuclear envelope reforms.
(e) Cytokinesis:
Results in __________ daughter cells.
Sources of Genetic Variation in Meiosis
1.
2.
Comparison of Mitosis and Meiosis
MITOSIS
MEIOSIS
Number of Divisions
Number of Daughter Cells
Ploidy of Daughter Cells
Cell Type
Genetic Variation?
I–
II –
I–
II –
What Aligns in
Metaphase?
What Separates in
Anaphase?
The Evolutionary Consequences of Sex
1. Random Fertilization
2. Importance for Evolution