Mitosis
and Meiosis
Mitosis: Cell Division


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In each human cell there are 23
unique chromosomes each containing
thousands of genes.
Most cells in the human body have 2
copies of every chromosome
These cells are called diploid (2n).
Mitosis

In order to keep the same genetic
information cells undergo a process of
division that ensures the same
information is passed from parent to
offspring.
A) Cell Cycle
A) Cell Cycle

The life cycle of a cell
has 2 portions:
Interphase and Mitosis.

Interphase is the normal
condition of a cell.
During this time the cell
does its job and
prepares for division.

Mitosis is the process of
division.
A) Cell Cycle

Interphase has 3 steps:



G1- The cell produces
proteins and performs
its normal functions in
the body.
S – DNA inside the
nucleus replicates.
G2 – The cell resumes
growth/function and
readies for division.
B) Mitosis

Mitosis is divided into 4 steps:





Prophase
Metaphase
Anaphase
Telophase
After Mitosis Cytokinesis occurs, which
is the division of the cytoplasm.
Mitosis: Prophase



The nuclear envelop
breaks down
Chromatin condenses
into chromosomes
(Xs)
Spindle fibers begin
migrating to opposite
ends.
Mitosis: Metaphase


The individual
chromosomes line up at
the center  metaphase
plate
Centrioles and spindles
are at opposite ends of the
cell and connected to
every pair of
chromosomes at the
centromere.
B) Mitosis: Anaphase

The centrioles pull
on the spindles
and separate the
chromatids to
opposite sides.
B) Mitosis: Telophase



The chromatids are
now in opposite ends
of the cell and they
begin to decondense.
Nuclear membrane
begins to reform.
Spindles break down.
B) Mitosis: Cytokinesis

In animals proteins
pinch off the center of
the cell into 2 each
parts, seperating the
cytoplasm.
In
plants the Golgi
synthesizes a new cell wall
along the metaphase plate,
creating 2 separate cells.
C) Meiosis


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In sex cells cell division is different.
The process must half the number of
chomosomes in each cell.
This allows for fertilization to recreate
the complete number of
chromosomes.
C) Meiosis


The process of meiosis is called a
reduction division.
There are 2 rounds of division with
some slight differences.
C) Meiosis
C) Meiosis

The first round of meiosis has the
following steps: Prophase I,
Metaphase I, Anaphase I, and
Telophase I.

The second round of division is made
up of: Prophase 2, Metaphase II,
Anaphase 2, and Telophase 2.
C) Meiosis

Differences:



During Prophase I homologous
chromosomes pair up at the metaphase
plate!
There is NO DNA duplication between
Meiosis I and II, so the DNA never has a
chance to double.
The end result is 4 haploid cells instead
of 2 diploid cells.
C) Meiosis