The 13/21 probe contains a mixture of unique DNA sequences that hybridize in the 13q14 region of chromosome 13, and unique DNA sequences complementary to the D21S259, D21S342 loci contained within the 21q22.13 regions on the long arm of chromosome 21.

Detects trisomy 13 (Patau syndrome) and trisomy 21 (Down syndrome) in prenatal diagnosis using amniotic fluid samples from high-risk pregnancies. Used for rapid chromosomal enumeration in suspected cases of chromosomal aneuploidies. Provides detection results in as little as 24 hours for efficient prenatal genetic screening and diagnosis.