A STABLE MARKER CHROMOSOME WITH A CRYPTIC CENTROMERE - EVIDENCE FOR CENTROMERIC SEQUENCES ASSOCIATED WITH AN INVERTED DUPLICATION

Centromere activation, an important mechanism in karyotype evolution, is occasionally observed in some human chromosome rearrangements. We r eport a possible occurrence of centromere activation in a marker chrom osome containing an atypical centromere associated with an inverted du plication of the region 14q32-->qter. The marker chromosome's reduced centromere lacks both the alpha and beta satellite sequences usually f ound at normal centromeres. In an attempt to identify the centromeric sequences, the marker chromosome was flow-sorted and amplified by a de generate oligonucleotide primer polymerase chain reaction. Reverse chr omosome painting experiments showed that the marker chromosome contain s sequences that are unique to the distal region of chromosome 14, as well as a low copy number of(centromeric) sequences that are also high ly represented in the centromeres of chromosomes 18 and 19. These data suggest the activation of a novel centromere in the 14q32-->qter regi on, very likely consequent to the duplication of the region itself.