title: A young girl with ring(18) mosaicism: cytogenetic studies and PEP A mapping.
abstract: A young girl with 46,XX,r(18)/46,XX/45,XX,-18 chromosome constitution is reported. She displays a slight degree of mental retardation. The line with the ring chromosome predominates in blood lymphocytes. In skin fibroblast culture the ring(18) line showed a constant decreasing trend, from 45% at the first passage, down to its disappearance at the 19th passage, where only 46,XX cells were observed. The child/mid parents' ratio of Peptidase A activity in red cells was 0.36. The Peptidase A activity in a fibroblast clone 46,XX,r(18) was 0.55 compared to the 46,XX line. These data suggest that the PEP A locus was lost in ring formation.
mesh_terms: D000293:Adolescent; D016282:Aspartic Acid Endopeptidases; D002869:Chromosome Aberrations; D002874:Chromosome Mapping; D002902:Chromosomes, Human, 16-18; D010450:Endopeptidases / Q000235:genetics*; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure; D006801:Humans; D008214:Lymphocytes / Q000648:ultrastructure; D009030:Mosaicism
chemical_list: D010450:Endopeptidases; C022325:aspartic proteinase A; D016282:Aspartic Acid Endopeptidases