Meiosis Cell Division
Set up Cornell
A. What is Meiosis?
All organisms that reproduce sexually
undergo meiosis.
 Meiosis is cell division of sex cells to
produce gametes.
ex. Sperm and egg cells
 Two divisions (Meiosis I and II)
 Meiosis reduces the number of
chromosomes by half.
 Four daughter cells are genetically different
Mitosis: An Interactive Animation

B. Ploidy is the number of
chromosomes in a cell.
N= haploid = one set of chromosomes
2N = diploid = two sets of chromosomes
8N= octoploid = 8 sets
C. Diploid vs Haploid
Haploid cells
only have one
set of
chromosomes
Diploid cells
have two sets
of
chromosomes.
N = 23
2N = 23
Human egg
and sperm
cells have
23.
Chromosome number
Human liver
cells have 46.
D. Homologous Chromosomes



are a pair of chromosomes, one
maternal and one paternal.
Similar in size and shape
Correspond to the same genes/traits
height
dimples
Eye
color
A Tetrad is ….



A Pair of homologous chromosomes
Formed during Interphase I
Four chromatids all together!!
Tetrad
E. Where does Meiosis
happen?

Spermatogenesis (in the testicles of
males) and Oogenesis (in the ovary of
females).

Diploid Spermatogonia (pre-sperm
cell) and Oogongia (pre-egg cell)
divide and reduce by half, producing
Haploid sperm and egg cells.
Diploid 2N

Haploid 1N
Spermatogenesis
1N
2N
2N
Meiosis I
N
Meiosis
II
N
F. How are the four daughter cells
genetically different from the
parent cell ?

This is due to
Crossing Over
Synapse during
Prophase I
Mitosis vs Meiosis
Results in
Cells are
Occurs in
Mitosis
2 Diploid Cells
(2N)
Genetically
Identical
Somatic
(Body) Cells
Meiosis
4 Haploid
Cells (N)
Genetically
Different
Sex Cells
. How many phases in
meiosis?



2 divisions
Meiosis I has Interphase I, prophaseI,
metaphase I, anaphase I, and
Telophase I and cytokinisis.
Meiosis II, has I II, P II, M II, A II, T II
and cytokinisis.
Summary





Where does meiosis happen?
If an elephant has 50 chromosomes in his
skin cell, how may are in his sperm cell.
Describe spermatogenesis
What do the term diploid and haploid mean?
Why are the daughter cells genetically
different from the parent and from each
other?