A female new born infant having severe lower abdominal deformities is described. She has a 46, XX, del (18) (p1105) karyotype based on G-banding analysis. Her parents and two sisters are chromosomally and clinically normal.
Chinese hamster strain cells cultured in the presence of BrdU (5-bromodeoxyuridine) for two or three successive generations are used. After hypotonic treatment and ethanol-acetic acid fixation, the slides are incubated at 80°C for 5 min in 2 M NaCl solution which had been alkalified by heating in a Coplin jar for several hours, and then stained with Giemsa. The procedure has resulted in dark staining of unifilarly BrdU-substituted (TB) chromatids and light staining of bifilarly substituted (BB) ones. The results of Feulgen staining are compatible with those of the Giemsa staining. This differential staining can reciprocally be converted by subsequent treatments with HCl followed by Giemsa staining to the type in which the BB-chromatids stain more intensely than the TB-chromatids.
Newborn mouse DNA was digested with a restriction endonuclease EcoRI and concentrated with respect to ribosomal RNA sequences by an RPC-5 column. DNA fragments of 14-17 kilobases in length, most probably containing promoter region of the ribosomal RNA gene, were used for cloning with λgt WES•λB as a vector using an in vitro packaging technique. Several clones containing 18S rRNA sequences were obtained. One of the clones which was transferred to a plasmid pBR322 (designated as pMrEL-1) was 14 kilobases in length, having only a part of 18S rRNA sequence. These results strongly suggest that this fragment carries a promoter region of the ribosomal RNA gene.