Chromosome Enumeration Probes are designed for identification and enumeration of human chromosomes in interphase cells and as an adjunct to standard karyotyping in metaphases. The Chromosome X & Y Control probe hybridizes near the centromeric region of chromosome X and chromosome Y, and is labeled using fluorescence in situ hybridization in orange and green. The Chromosome X & Y Control probe is ideal for enumerating chromosome X and chromosome Y. In a normal interphase nucleus, two signals are expected using Chromosome Enumeration Probes specific for autosomes. Using chromosome Y specific probes will result in normal male cells in one signal and in normal female cells in no signal. Using chromosome X specific probes will result in normal male cells in one signal and in normal female cells in two signals per nucleus. Other signal patterns indicate numerical aberrations of the respective chromosome.