Unequal cross-over is involved in human alpha satellite DNA rearrangementson a border of the satellite domain

It can be invoked from the theory of tandem repeat homogenization that DNA on a satellite/non-satellite border may carry sequence marks of molecular p rocesses basic to satellite evolution. We have sequenced a continuous 17-kb alpha satellite fragment bordering the non-satellite in human chromosome 2 1, which is devoid of higher-order repeated structure, contains multiple re arrangements, and exhibits higher divergence of monomers towards the border , indicating the lack of efficient homogenization. Remarkably, monomers hav e been found with mutually supplementary deletions matching each other as r eciprocal products of unequal recombination, which provide evidence for une qual cross-over as a mechanism generating deletions in satellite DNA. (C) 1 998 Federation of European Biochemical Societies.