A simple and reliable method of chromosome banding for prenatal cytogenetics using a bromodeoxyuridine pulse.

An extremely simple, fully defined and reliable technique for banding chromosomes in situ is described. The method uses a pulse of bromodeoxyuridine to produce replication pattern banding complete with G- and C-type banding in the same karyotype. This enables immediate resolution of problems otherwise requiring extra subculturing and the application of conventional banding techniques. The value of routine chromosome banding in prenatal cytogenetics using such an economical technique is discussed.

Non C-banding variants in some normal families might be homogeneously staining regions.

Three families are reported showing transmission of a previously described variant, which is not associated with any clinical abnormality. The variant involves additional material at the band 9p12, which shows homogeneous staining of intermediate density with GTL- and RBG-banding, and negative staining with CBG-banding. The region stains positively with Feulgen stain. In situ hybridization with total genomic human DNA, cloned alpha satellite, satellite III, and ribosomal DNA all show no hybridization to the 9p12 variant. Two members of one of the families show the largest 9p12 variant yet reported; two other carriers in this family have inherited a variant of decreased size. It is suggested that the 9p12 variants are homogeneously staining regions. Using the ISCN three-letter convention, this variant could be described as hsr(9)(p12).

Extra embryonic/fetal karyotypic discordance during diagnostic chorionic villus sampling.

From a total of 1312 diagnostic chorionic villus samplings (CVS) there were 22 which showed discordance between the karyotype of the chorionic villi and that of the fetus. This frequency was some 20-fold higher than that reported at amniocentesis. In the majority of discordant cases, the fetal karyotype was normal while the placental karyotype was mosaic. In four cases, the placental karyotype was non-mosaic (a trisomy 16, a monosomy X, and two tetraploids) while the fetal karyotype was normal. In one case, the placenta was trisomy 18 while the fetus was mosaic. There were two 'false-negative' results where short-term methods showed only normal cells while both long-term cultures of chorionic villi and fetal cells were mosaic, in one 46,XY/47,XXY and in the other 46,XY/47,XY,+21.