title: Human inherited marker chromosome 22 short-arm enlargement: investigation of rDNA gene multiplicity, Ag-band size, and acrocentric association.
abstract: The banding characteristics of an extreme variant familial chromosome 22 short-arm enlargement are described. Ag-AS staining for nucleolar-organizer regions, identified two areas of rDNA actively coding for 18S and 28S rRNA, the one being a broad distal Ag-band and the other a narrower centromeric Ag-band. The DNA in the major portion of the enlarged short arm was highly methylated, as shown by the binding of antibodies to 5-methylcytidine after UV-denaturation of chromosomal DNA. Mean Ag-band size on the aberrant 22p+ correlated with the mean number of 22p+ associations. Association of 22p+ was no greater than that of other acrocentrics, in spite of a presumed excess number of rDNA gene copies. This case represents only the second such normal variant defined by these techniques.
mesh_terms: D002455:Cell Division; D002648:Child; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002904:Chromosomes, Human, 21-22 and Y; D004247:DNA / Q000235:genetics*; D005796:Genes; D005815:Genetic Code; D005819:Genetic Markers; D014644:Genetic Variation; D006801:Humans; D007621:Karyotyping; D008297:Male; D009697:Nucleolus Organizer Region; D010641:Phenotype; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012834:Silver
chemical_list: D005819:Genetic Markers; D012335:RNA, Ribosomal; D012834:Silver; D004247:DNA