SINE AND LINE WITHIN HUMAN CENTROMERES

A number of the Alu and L1 elements present within the centromeric reg ions of the human chromosomes have been analyzed by polymerase chain r eaction amplification. The oligonucleotide primers were homologous to the 3' end consensus sequences of either Alu or L1 in conjunction with an oligonucleotide primer homologous to alphoid sequences specific to different chromosomes. This allowed one to detect an unusual number o f Alu and L1 polymorphisms at different loci. It is proposed that this results from molecular rearrangements which occur within the a-satell ite DNA in which they are embedded (Marcais et al. J. Mol. Evol. 33:42 -48, 1991) and not because the centromeric regions are targets for new insertions of such elements. The same analyses were made on cosmids a nd YACs originating from the centromeric region of chromosome 21 as we ll as on a collection of somatic hybrids containing chromosome 21 cent romere as unique common human genetic material. The results were consi stent with the above hypothesis.