title: Validation of DNA probes for molecular cytogenetics by mapping onto immobilized circular DNA.
abstract: BACKGROUND
  Fluorescence in situ hybridization (FISH) is a sensitive and rapid procedure to detect gene rearrangements in tumor cells using non-isotopically labeled DNA probes. Large insert recombinant DNA clones such as bacterial artificial chromosome (BAC) or P1/PAC clones have established themselves in recent years as preferred starting material for probe preparations due to their low rates of chimerism and ease of use. However, when developing probes for the quantitative analysis of rearrangements involving genomic intervals of less than 100 kb, careful probe selection and characterization are of paramount importance.
  
  
  RESULTS
  We describe a sensitive approach to quality control probe clones suspected of carrying deletions or for measuring clone overlap with near kilobase resolution. The method takes advantage of the fact that P1/PAC/BAC's can be isolated as circular DNA molecules, stretched out on glass slides and fine-mapped by multicolor hybridization with smaller probe molecules. Two examples demonstrate the application of this technique: mapping of a gene-specific ~6 kb plasmid onto an unusually small, ~55 kb circular P1 molecule and the determination of the extent of overlap between P1 molecules homologous to the human NF-kappaB2 locus.
  
  
  CONCLUSIONS
  The relatively simple method presented here does not require specialized equipment and may thus find widespread applications in DNA probe preparation and characterization, the assembly of physical maps for model organisms or in studies on gene rearrangements.
authors.affiliation: Division Genetics of Skin Carcinogenesis, German Cancer Research Center (DKFZ), Heidelberg, Germany. k.greulich@dkfz-heidelberg.de.
authors.forename: Karin M
authors.initials: KM
authors.lastname: Greulich-Bode
authors.forename: Mei
authors.initials: M
authors.lastname: Wang
authors.forename: Andreas P
authors.initials: AP
authors.lastname: Rhein
authors.forename: Jingly F
authors.initials: JF
authors.lastname: Weier
authors.forename: Heinz-Ulli G
authors.initials: HU
authors.lastname: Weier