Confirmation of the PRINS technique specificity. (A) Telomere-specific signals. A 50-bp oligonucleotide designed to anneal to the repeated sequences of human telomeres was used for PRINS on a female human metaphase chromosomal spread. The green PRINS signals were detected at the telomeres of all human chromosomes. (B) X chromosome centromere-specific signal. A 50-bp oligonucleotide designed to anneal to a portion of the human X chromosome located at the centromere was used for PRINS on a female human metaphase chromosomal spread. Only two green PRINS signals were detected. These signals were located at the centromeres of the X chromosomes.