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DNA Isolation
Where is the DNA?



Eukaryotes (that is
us!) have nucleated
cells.
The nucleus contains
chromosomes made
out of DNA.
What about
organisms that don't
have a nucleus?
Where is their DNA?
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure

This is a hypertonic solution.→
(high concentration outside cell)
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure


The concentrations outside
of the cell and inside of the
cell will try to balance.
Water will run out of the cell,
and it will shrivel up.
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure

This is a hypotonic solution. →
(low concentration outside cell)
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure


The concentrations outside
of the cell and inside of the
cell will try to balance.
Water will run in to the cell,
and it will swell.
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure


The concentrations outside
of the cell and inside of the
cell will try to balance.
Or burst.
Step 1: Cells in Solution

Peas + blender → cell soup

Why are we adding salt?

Osmotic Pressure


If our solution has just the right
number of molecules dissolved, it
will match the concentration of
the cell.
This is an isotonic solution.→
(Now, everyone is happy.)
Step 2: Removing the Membranes

Plasma membrane

Nuclear membrane

Bilayers

Hydrophilic = water loving

Hydrophobic = water fearing
Step 2: Removing the Membranes

Detergent

Breaks down membranes

Also breaks down some proteins
Step 3: Eliminating the Proteins

Histones


Nucleases


Stuck to DNA
Will destroy your DNA
We will use a
protease to chew up
the proteins in
solution.
Step 4: Separating the DNA

Isopropyl Alcohol


Will precipitate DNA
Water

Will dissolve DNA