Characterization ofThreeDeNovoDerivative Chromosomes 16by"Reverse ChromosomePainting" andMolecular Analysis

Summary Wehaveanalyzed three denovo chromosome 16rearrangements-twowith a 16p+chromosome andone a 16q+-none ofwhich could befully characterized byconventional cytogenetics. Ineach case,flow karyotypes havebeenproduced, andtheaberrant chromosome hasbeenisolated byflow sorting. Theorigin ofthe additional material hasbeenascertained byamplifying andlabeling theDNA oftheabnormal chromosome by degenerate-oligonucleotide-primer-PCR andhybridizing itinsitu tonormal metaphase spreads (reverse chromosome painting). Both16p+chromosomes contain more than30Mb ofDNA fromtheshort arm of chromosome 9(9p21.2-pter), while the16q+contains approximately 9MbofDNA from2q37. Thebreakpoints on chromosome 16havebeenlocalized ineach case;the twobreakpoints on theshort arm areatdifferent points within theterminal band, 16p13.3. Thebreakpoint on thelong arm ofchromosome 16is veryclose to(within 230kbof)the16qtelomere. Determination oftheregions ofmonosomy andtrisomy allowed theobserved phenotypes tobecompared withother reported casesinvolving aneuploidy forthese regions.