Primers used were as described previously [14,15]. PCR was performed in a 25 μl reaction mixture containing 1× PCR buffer, 1 U Taq polymerase (Invitrogen Corporation), 20 ng of each primer pair, 1.5 mmol/l MgCl2, 200 μmol/l each dNTP and 50 ng of DNA template.
PCR thermocycling (conducted in TProfessional standard thermocycler; Biometra GmbH) conditions were as follows: 95 °C for 5 min; 35 cycles of 95 °C for 60 s, 56–62 °C (depending on Tm of the primer pair) for 45 s and 72 °C for 45 s; and a final step of 72 °C for 5 min.
Then 5 μl aliquots of the amplicons were digested with 5 U of the appropriate restriction endonuclease in a 10 μl reaction volume at 37 °C for 3 h. A 5 μl aliquot from each of the reaction mixture was analyzed by 3% agarose gel-electrophoresis, and the DNA fragments were stained with ethidium bromide and visualized under UV light.