The XA 13/21 mix of specific probes allows detecting copy number variations for chromosomes 13 and 21. The green labeled probe hybridizes to a region at 13q14 including the RB1 locus and the orange labeled probe hybridizes to a region at 21q22 including the DSCR4 (Down syndrome critical region 4).

Probe maps are created in accordance with the intended purpose of the product. Solid colored bars do not necessarily indicate that the probe fully covers the indicated genomic region. Therefore, caution is advised when interpreting results generated through off-label use. Probe map details based on UCSC Genome Browser GRCh37/hg19. Map components not to scale. Further information is available on request.

Numerical aberrations of autosomes 13, 18, 21, and sex chromosomes X and Y account for 95% of birth defects in newborns. FISH applied to uncultured amniocytes provides a method to identify those aberrations much faster than conventional chromosome analysis. It has become a standard to provide preliminary results for the detection of anomalies in less than 12 hours.

Duplications of chromosome bands q22.13-q22.2 have been shown to define the smallest region implicated in the causation of Down syndrome. Trisomy 13 syndrome is a rare chromosomal disorder in which all or a portion of chromosome 13 appears three times (trisomy). Based on molecular results, a region ranging from 13q14-13qter has been found to be critically involved in Patau syndrome.

XA 13/21 was hybridized to normal lymphocytes. Interphase nuclei with two orange and two green signals each are shown.

• Bryndorf et al (1996) Am J Hum Genet 59:918-926
• Tepperberg et al (2001) Prenat Diagn 21:293-301
• Stumm et al (2006) Cytogenet Genome Res 114:296-301