Download Mitosis - Olympic High School

Mitosis
[Remember: Mitosis happens in
my toesies]
Purposes of cell division
1. Increase the number of cells for growth
and repair of worn out tissues (mitosis)
2. Transmit genetic information (DNA) to
other cells
•
We will study transmitting DNA to other
generations later: Reproduction and
heredity
Mitosis: One cell becomes two
• Each daughter
cell gets exactly
the same DNA.
• Mitosis goes on in
all parts of a
Eukaryotes body.
• Prokaryotes use a
different method
— “Binary fission”
to divide.
Chromosomes are coiled strands of
instructions (DNA)
This is a chromosome
in the “mother” cell
This is also called a
chromosome, but it has
doubled itself so that
there is one copy for
each “daughter” cell.
These are the
“daughter” cells and
each has its own
copy of all the
DNA—They are
clones of the
“mother” cell and
identical to each
other in all ways.
This is an actual
image of a
chromosome that
has both copied
itself and coiled
up into this nice
fluffy shape.
Clearing up the confusion!
Remember, even
though it is doubled
they still call it
a chromosome!
The two copies are called
sister chromatids
It’s the same DNA; just at different
stages of the cell cycle.
Here the DNA is not as
coiled so the ENTIRE
nucleus is colored
when the DNA is
stained.
Here the DNA is coiled
tighter so only the
chromosomes are
colored and visible.
Chromosomes and Genes
•
•
A gene is a short
length of DNA on a
chromosome which
controls an inherited
characteristic of the
organism (It is the
instruction for a single
protein)
A chromosome
carries a lot of genes
(it is more like an
instruction book)
gene controlling skin
colour
gene controlling
tongue rolling
chromosome
gene controlling
eye colour
gene controlling
blood group
Our Chromosomes: From uncoiled
to coiled
Each Human cell has 46
chromosomes
• 22 pairs are essentially identical in both sexes
One from Mom, one from Dad. Autosomes
• The 23rd pair is different in males (They have an
X and a Y chromosome) and females (they have
two X’s). Sex chromosomes.
Other species have
different numbers of
chromosomes:
Horse - 64
A fern species - 1200
Flatworm - 16
Fruit Fly - 8
Male ants - 1
2 major parts of the cell cycle
• The cells grow, lots of extra proteins
are made, and organelles (such as
the mitochondria) and DNA replicate
to prepare for cell division.
• The cell divides (mitosis) resulting in
two identical daughter cells (clones).
The Cell Cycle
• Cells are either Growing
– (G phase)
• Synthesizing new DNA
– (S phase)
• 0r dividing by Mitosis
– (M phase)
• M phase has four parts:
– Prophase, Metaphase,
Anaphase and Telophase.
• The G and the S phases are
collectively called the
Interphase
Interphase (Resting and
growing stage)
• Chromosomes
cannot be seen.
• Cells grow.
• Chromosomes
duplicate.
• How do the
chromosomes
duplicate?
Prophase
nuclear
membrane
chromatids centromere
disappearing
• Chromosomes
condense and
become visible
• Each chromosome
consists of two
identical sister
chromatids.
homologous
chromosomes
Metaphase
• Chromosomes line
up at the equator
(centre of the cell)
• Spindles are
formed to attach to
the center of each
chromosome
Anaphase
• Sister chromatids
separate as
individual
chromosomes
• They move apart
towards the
opposite poles
chromosomes
Telophase
nuclear membrane
forming
• Chromosomes
gradually disappear
• Nuclear membrane
is formed around
each set of
chromosomes
Summary of Mitosis
Prophase
• In prophase, the cell
begins the process
of division and
chromosomes
condense.
Metaphase
• In metaphase the
chromosomes line
up on the equator
of the cell
Anaphase
• In anaphase, the
centromeres
divide.
• Each half of the
cell gets a single
chromatid.
Telophase
• In telophase the
chromosomes are at
the poles of the cell.
• Then the cytoplasm
divides into 2
separate cells.
Summary of Mitosis
• Prophase:
• Chromosomes condense and are visible
• Nuclear membrane disappears
• Metaphase
• Chromosomes lined up on equator of cell
• Anaphase
• Chromosomes divide and are pulled to
opposite poles of the cell
• Telophase
• Chromosomes disappear and Cytoplasm
divided into 2 cells
• New nuclear membranes are also formed.
Cancer
• Cancer is a disease of uncontrolled
cell division.
• It starts with a single cell that loses
control of the cell cycle due to a DNA
mutation in gene for a protein that
controls that cycle.
• That cell starts dividing without limit,
and eventually can kill the host.
Can you identify the different stages
of mitosis from the diagram below?
anaphase
interphase
telophase
metaphase
prophase
A Review
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
At which stage is there most protein production?
At which stage do the chromosomes line up at the cell equator?
At which stage do the chromosomes become visible?
At which stage do the chromosomes replicate?
At which stage does the nuclear membrane re-appear?
At which stage do the Sister Chromatids separate?
At which stage does the nuclear membrane disappear?
Is Chromosome 13 from Mom identical to C13 from Dad?
What is a Gene?
Are the genes on Sister Chromatids identical?