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  Stuck to DNA Nucleases  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