A method of preparing an immobilized oligonucleotide having a free 3'-end
comprises the steps of: i) preparing an oligonucleotide attached in a
first position to a solid support via its 3'-end and having a free 5'-end;
ii) binding said oligonucleotide in a second position remote from the
3'-end to the solid support; and iii) selectively releasing the 3'-end of
the oligonucleotide from the solid support to obta the oligonucleotide
attached to the support in said second position in a reversed orientation
with a free 3'-end.
