FISH

• Detects the presence of a DNA sequence within a set of metaphase chromosomes or the interphase nucleus.
• Maps the hybridization location according to chromosome band.
• Detection sensitivity
  • greater than 10 kb - routine
  • 1 to 5 kilobases - challenging
• Chromosome painting with fluorescent labeled chromsome libraries is valuable in defining rearrangements that are not clearly deciperable by G-band analysis

A probe to the elastiin gene ELN is diagnostic for the deletion seen in 90% of Williams Beuren Syndrome patients. Chromsomes 7 are clearly identified for scoring by hybridization with probe to D7S in 7qThe deletion is seen in GM13481.

A probe maps to the distal end of mouse chromosome 11. Inversion of the DAPI counterstain facillitates identification of when the expected site of hybridization is unknown and no control probe is available before the experiment.