Physical map around the retinoblastoma gene: possible genomic imprinting suggested by NruI digestion

A long-range restriction map constructed around the retinoblastoma (RB) gene by means of PFGE analysis allowed further definition of chromosomal rearrangements with a breakpoint within the gene, as well as of submicroscopic deletions. A serendipitous observation was that the NruI restriction pattern differs according to the parental origin of the rearrangement.