The 1q21.1 area, one of the largest regions in the human genome, is highly susceptible to copy number variation due to its frequent low-copy duplications.

Whole exon sequencing and quantitative polymerase chain reaction can provide a precise molecular diagnosis for children with 1q21.1 microduplication syndrome.

The findings that are most frequently recorded include frontal bossing, hypertelorism, and (relative) macrocephaly.

[2] The 1q21.1 area is one of the largest regions in the human genome with repetitive duplication, rendering it prone to copy number variation.

There are two main ways that the copy number variations of 1q21.1 might appear: Type I, which spans roughly 1.8 Mb and includes only the distal end area of 1q21.1, and type 2, which extends proximally to include the thrombocytopenia absent radius syndrome region, span around 2.7 Mb.

[9][1] For children with 1q21.1 microduplication syndrome, whole exon sequencing in conjunction with quantitative polymerase chain reaction can yield a precise molecular diagnosis.

Further research confirmed that the odds on a relation between schizophrenia and deletions at 1q21.1, 3q29, 15q13.3, 22q11.21 en Neurexin 1 (NRXN1) and duplications at 16p11.2 are at 7.5% or higher.

[15] GJA5 has been identified as the gene that is responsible for the phenotypes observed with congenital heart diseases on the 1q21.1 location.