Chromosome Enumeration Probes are designed for identification and enumeration of human chromosomes in interphase cells and as an adjunct to standard karyotyping in metaphases. These probes will produce sharp, bright signals specific for each individual chromosome.

As several chromosomes share the same repetitive sequences resulting in cross-hybridization signals, they cannot be differentiated by centromere specific probes. Instead, these chromosomes can be identified by direct labeled Specific Probes hybridizing in close proximity to the respective satellite DNA sequences or to other chromosome specific loci.

The 4p11 Probe is designed to hybridize in close proximity of centromere 4 at 4p11 harboring the ZAR1 (zygote arrest 1) gene. ZAR1 is an oocyte-specific gene that appears to function at the oocyte-to-gamete transition. For an unambiguous enumeration of chromosome 4 the SPEC 4p11 is found to be more suitable.