All individuals with 18p deletions that were the result of inherited unbalanced translocations or other rearrangements were excluded from the analysis.

Only nonmosaic patients with de novo deletions of 18p were included in the study.

We demonstrate the presence of a possible breakpoint cluster on the short arm of chromosome 18 and the absence of a parent-of-origin bias for terminal de novo deletions, regardless of where on the chromosome the deletion occurs.

Sw 1976 satx adult chat-26

We are interested in understanding the molecular basis of the clinical characteristics in this syndrome.

Detailed molecular analyses were used to ascertain the size and parental origin of the deletion in each subject.

Cody, Ph D, Department of Pediatrics, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-7809.

Received 22 June 2001; Accepted 16 October 2001Purpose: To determine the size and parental origin of the deletion in individuals with 18p− syndrome.

Twenty-five subjects with deletions of 18p were recruited from The Chromosome 18 Registry and Research Society.

Written informed consent was obtained for all subjects under an institutional review board-approved protocol.Developmental differences between oogenesis and spermatogenesis may give rise to a parent of origin bias in individuals with chromosomal abnormalities.The paternal bias in structural rearrangements is thought to be due to the greater number of cell divisions during male meiosis, as well as minimal repair capacity in sperm.First, there can be differences in the origin of the deletion, dependent on the sex of the parent.Parental origin biases in mutation rates were reviewed by Chandley.Methods: Molecular and fluorescence in situ hybridization analyses of the pericentromeric region of chromosome 18 were performed on genomic DNA and chromosomes from study participants.