From Balbiani's Rings to Partial Trisomy

Nowhere in science is the time lag between basic discoveries and their application to the human organism better illustrated than in the field of cytogenetics. Elsewhere in this issue are reported two studies of the chromosomal and phenotypic manifestations of partial trisomy 13 in man. Escobar et al (see page 217) describe a patient having a new syndrome associated with trisomy of the distal segment of chromosome 13, and Escobar and Yunis (see page 221) delineate the clinical findings in a child with trisomy for the proximal segment of the long arm of chromosome 13. The development of banding techniques for human chromosomes over the last three years has permitted an analysis of intrachromosomal changes hitherto impossible. From their Giemsa banding studies, Escobar et al postulate the formation of a meiotic inversion loop in the mother, with the affected child receiving a recombinant chromosome having two bands duplicated, and thus