Isolation of DNA fragments

But how do you get the fragment back out of the gel???

Old Methods
Gel slab squeeze (French press)
Chop, soak and spin
Filter spin

All give poor yields as often agarose retains the DNA

Electrophoresis onto dialysis membrane
    Elution into a dialysis bag under current followed by precipitation.
    Low yield

Low melting point agarose
    This agarose can be dissolved at a temperature that does not denature the DNA
 
Modern Methods
Dissolving the agarose with a high concentration of NaI (~50 C) and recovery
1) binding to glassmilk and centrifugation
    Shearing of fragments larger than 3-4 kb is  major problem
2) binding to DNA isolation spin column.
    Little shearing
 

Protocol