1. Department of Pediatrics, Genetics Unit, and Program in Human Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
2. Department of Biostatistics, Human Genetics Program, University of Pittsburgh, Pittsburgh, PA 15261. P. C. Watkins, Integrated Genetics Inc., Framingham, MA 01701.
3. First Department of Pediatrics, Cytogenetics Unit, Athens University Medical School, Athens, Greece.