Variant-specific oligonucleotide probes distinguish homologous chromosomes by FISH. (A) Three classes of chromosome 15 are identified by the oligoprobes: those positive for 15VAR1.4 only (green; left panel), those positive for 15VAR2.4 only (red; center panel), and those positive for both 15VAR1.4 and 15VAR2.4 (yellow; right panel). (B) 15VAR1.4 (signal in green) hybridizes to both chromosomes from this individual (father in pedigree from panel C), while 15VAR2.4 (signal in red) hybridizes only to one. (C) 15VAR1.4 and 15VAR2.4 were used to follow the transmission of a single chromosome from parents to offspring. Half-shaded symbols, 15VAR1.4/15VAR2.4 heterozygotes; shaded symbol, 15VAR2.4 homozygote.
