XA 13 / 21

Aneusomy Probe

Order Number
Package Size
100 µl (10 Tests)


XA 13 / 21

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 map details based on UCSC Genome Browser GRCh37/hg19. Map components not to scale.

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Clinical Details

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 from 13q14-13qter has been found to be critically involved in Patau syndrome.

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XA 13 / 21

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

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Expected Patterns

Expected Pattern 1

Normal Cell:
Two green (2G) and two orange (2O) signals.

Expected Pattern 2

Aberrant Cell: Trisomy 13
Three green (3G) and two orange (2O) signals.

Expected Pattern 3

Aberrant Cell: Trisomy 21
Two green (2G) and three orange (3O) signals.

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  • 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