Cell Division—
Mitosis Notes
Why do Cells Need to
Divide?
• Transport of materials in and out of the cell
is MUCH FASTER over short distances.
• DNA codes the proteins our cells need to
survive. The larger the cell, the more protein
it would need and DNA could not keep up!
• Surface Area to Volume Ratio – the larger
the cell, the more volume it has. More is
needed and more waste is produced. It
would need more surface area than the
membrane could provide.
Why do cells need to
divide?
Living things grow by producing more
cells, NOT because each cell increases in
size

Cell Division — process
by which a cell divides
into 2 new cells

Remember from the cell theory
that all cells come from
preexisting cells, so genetic
information has to be passed
from one generation to the
next.
Cell Reproduction
Genetic information is contained
in DNA – deoxyribonucleic acid
which is in the nucleus of a cell.
 DNA exists in the nucleus as
long, threadlike strands called
chromatin.
 When a cell is going to divide
and produce more cells, the
chromatin winds up into a
double, coiled structure called a
chromosome.

Cell Reproduction
Cell Reproduction
All cells of the body EXCEPT the
sex cells are called somatic cells.
 Blood cells, nerve cells, skin
cells, etc.
 New somatic cells are made
when one parent cell divides
into two identical daughter cells

Cell Division
The Cell Cycle: The process
somatic cells go through in
order to grow and reproduce
The cell cycle is divided into
two main parts:

Interphase
 Mitosis (M Phase)

Cell Division
Interphase– this is a time of
growth and a time when
DNA is replicated (a copy is
made) inside the nucleus of
the cell

Interphase
G1 Phase – G is for GROWTH! The
cell is growing and making proteins
 S Phase – S is for SYNTHESIS
(making something). This is when
the DNA is replicated and an
identical set of chromosomes is
made
 G2 Phase – G is for GROWTH. The
cell continues to grow and is getting
ready for mitosis (division)

Interphase
Mitosis is when the nucleus
divides
The second part of the cell
cycle is mitosis and
cytokinesis.
Cytokinesis is when the
entire cell divides

Mitosis
Mitosis is divided into 4
phases:
Prophase
Metaphase
Anaphase
Telephase

Mitosis
The chromatin coils up tightly, gets
shorter and thicker, and can be seen
in the nucleus.
 The chromatin is lined up in a way
that two sister chromatids are held
together at a middle point called a
centromere. Each sister is a duplicate
of the other (this was done in S
phase).

Prophase
Prophase
The nuclear membrane
disintegrates and a
spindle starts to form.
 Spindle – Microtubules
that line up in a spindle
form in the cell to help
division

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Chromatids line up
in the MIDDLE.
 They attach to the
spindle at the
centromere in the
middle of the nucleus
(equator)

Metaphase
https://commons.wikimedia.org/wiki/File:Mitotic_Metaphase.svg

Chromatids are
pulled apart by the
spindle. Each
chromatid is now its
own chromosome
Anaphase
http://www.proprofs.com/flashcards/story.php?title=pratical-
The chromosomes reach
opposite ends of the cell and
start to unwind.
 Spindle disappears
 Two new nuclear membranes
form around each set of
chromosomes to form two new
nuclei

Telophase
Telophase
http://home.apu.edu/~jsimons/Bio101/genetics.htm

The cytoplasm divides during
cytokinesis
Cytokinesis
http://www.celldynamics.org/celldynamics/research/cytokinesis/inde
In plant cells, a cell plate
forms between the two nuclei
and grows out to the edges,
dividing the cell in half.
In the plant cell, a new cell
membrane will form around
each cell and a cell wall forms
around the outside.

Plant vs Animal
Interphase
G1-Growth
S-Synthesis-DNA
Replication
G2 - Growth
M Phase
(Mitotic)
Prophase –
Chromatin
Condenses
Metaphase –
Chromatids line up
in the middle
Anaphase –
Chromatids separate
Telophase – New
nuclear membranes
Identify the Following
Stages of Mitosis!
What is the longest part of the
cell cycle?
Interphase
In which part of interphase
are the chromosomes
replicated?
S Phase
During what part of interphase
does the cell grow and prepare
for mitosis?
G2
What is the division of the
nucleus called?
Mitosis
What is the division of the
entire cell called?
Cytokinesis
If you are observing a cell and
notice that the chromosomes
appear to be lined up in the
middle of the nucleus, what
stage of mitosis are you
observing?
Metaphase
If it looks as though the cell you
see through the microscope has
two nuclei, what stage of mitosis
are you observing?
Telophase
A cell plate is forming in one of
the cells that you are observing.
Which of the following type of
cells could you be viewing?
a. Human skin cells
b. Root tip cells
c. A fly’s eye
d. bristles of an earthworm
Root tip cells!
In which of the following
circumstances would cells NOT
divide by the process of mitosis?
a. Repairing a cut
b. Adding cells for an infant to
grow
c. Creating sex cells
d. Replacing old skin cells
Creating sex cells
How many times do
chromosomes separate during
the process of mitosis?
One
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