Science Starter #4 – 12/15/16
 What are the three parts of interphase?
 What are the four parts of mitosis?
 List all parts of the cell cycle
 TURN IN YOUR CELL PREVIEW
Chapter 8
pg. 161-164
Meiosis
 Two rounds of cell division (two rounds of “mitosis”)
 Results in FOUR haploid cells (1n); gametes
 One 2n cell two 1n cells four 1n cells
 Two stages of meiosis (I and II)
Meiosis I
 Similar to the phases of mitosis
 One 2n cell  Two 1n cells
 Separating HOMOLOGOUS CHROMOSOMES in four phases

Prophase I, Metaphase I, Anaphase I, Telophase I
Meiosis I – Special Occurrences
 Two important things occur in meiosis I that do not
occur in mitosis

crossing over
and
independent assortment
Crossing Over
 Synapsis: chromosomes line
up with homologues to make
a tetrad
 Crossing-over: random
exchange of genetic material
during PROPHASE I
 HOMOLOGOUS PAIRS
overlap and twist on each
other
 Increases genetic diversity
Independent Assortment
 Independent assortment: random separation of
HOMOLOGOUS CHROMOSOMES during
ANAPHASE I
 Increases genetic diversity
Meiosis I
 Metaphase I
 Homologous pairs move
together along the
middle
 Anaphase I
 Homologous pairs are
pulled apart
 End Product – Two 1n
cells.
Meiosis II
 Meiosis II: begins right after meiosis I (DNA not replicated)
 Two 1n cells  Four 1n ; 4 haploid cells (genetically different)
 Separating SISTER CHROMATIDS
 Prophase II, Metaphase II, Anaphase II, Telophase II
Meiosis is the formation of Gametes
 Spermatogenesis (testes): males produce four sperm cells
 Oogenesis (ovaries): females make one egg and 3 polar
bodies
Homologous chromosomes are
separated during (meiosis I) or
(Meiosis II)?
Sister Chromatids are separated
during (meiosis I) or (Meiosis II)?
Mitosis
Cell Division
Number of Cells Made
Nuclear State of cell Made
Chromosome # (for humans)
Type of Cell Made
(gamete or somatic)
Genetically unique or identical?
Picture
Meiosis