Isopropanol vs EtOH

[Rob Kirkpatrick]

Howdy,

Does anyone know why isopropanol is used to precipitate DNA in some
cases (i.e. after column purification) while Ethanol is used other
times?  I'm told it has do do with yield (EtOH is better?) and purity
(isopropanol is better?).  Also, while we're at it, why do we sometimes
use Sodium Acetate and other times use Ammonium Acetate to aid in
precipitation?

Thanks in advance!

Rob