ABSENCE OF LAMBDA-IMMUNOGLOBULIN SEQUENCES ON THE SUPERNUMERARY CHROMOSOME OF THE CAT-EYE-SYNDROME

The supernumerary bisatellited chromosome causing the ''cat eye'' synd rome (CES) is of chromosome 22 origin and consists of an inverted dupl ication of the 22pter--> 22q11.2 region. To determine the extent of in volvement of band q11.2 on the bisatellited chromosome, copy number as sessment of sequences homologous to cloned lambda immunoglobulin (lamb da Ig) gene region probes was carried out on DNA from individuals with CES using densitometric analysis of Southern blots. None of the 10 la mbda Ig sequences studied was found in increased copy number in DNA fr om any of the 10 CES individuals tested, indicating that these sequenc es are not present on the supernumerary chromosome. The breakpoints in volved in the generation of the bisatellited supernumerary chromosome associated with CES are therefore proximal to the lambda Ig gene regio n. (C) 1995 Wiley-Liss, Inc.