The use of sequential silver and quinacrine staining to determine the parental origin and breakpoints of a ring‐22 human chromosome

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Abstract
A G-ring syndrome discovered in 1968 was suggested to be due to a ring-22 (Weleber et al., 1969). In 1972, the ring was found to be derived from chromosome 22 (Magenis et al., 1973). A new case of the ring-22 syndrome is reported in a child with clinical findings virtually identical to those described earlier. By sequential staining techniques with Ag and quinacrine, it was possible to determine the parental origin of the ring (maternal) and to estimate the breakpoints in the chromosome 22 (22p12 and 22q13) leading to the ring configuration. The clinical abnormalities are due to terminal deletion of 22q distal to the breakpoint in band 22q13. The Ag technique, especially in sequence with other stains, provides new and useful data concerning the origin and precise cytology of this, one of the tiniest rings known in humans.