Chorionic villus metaphase chromosomes and interphase nuclei analysed by chromosomal in situ suppression (CISS) hybridization.

Metaphase chromosomes and interphase nuclei of chorionic villus samples (CVS) in five cases were studied after treatment with trypsin and post-fixation in formaldehyde by chromosomal in situ suppression (CISS) hybridization. Our modified protocol enables the use of in situ hybridization techniques on CVS preparations after 42 h of culture. A balanced translocation and trisomy 13 were identified with the aid of CISS hybridization.