The use of DNA probes to establish parental origin in Down syndrome.

Molecular analysis was performed to determine the parental origin of the extra number 21 chromosome in 20 couples following the birth of a child with standard trisomy 21. The parent of origin was successfully identified in 9 of 20 (45%) using five chromosome-21-specific DNA probes and eight restriction endonucleases by restriction fragment length polymorphism and dosage analysis; seven were of maternal and two of paternal origin. Utilizing the observed allele frequencies, the expected frequencies of informative homozygous matings [2(p2q2)] approximate 10% for seven of eight enzyme/probe combinations; the eighth, TaqI/pPW231F (D21S3), is 3%.

Micronucleus assay in human fibroblasts: a measure of spontaneous chromosomal instability and mutagen hypersensitivity.

By comparing fibroblast strains derived from individuals exhibiting chromosome instability and/or mutagen hypersensitivity (Cockayne syndrome, ataxia telangiectasia, and Fanconi anemia) with strains derived from healthy donors, the fibroblast micronucleus assay has been established as a reproducible measure of the genotypic variation in spontaneous or mitomycin C (MMC)-induced chromosomal instability. The patient strains that were moderately or exquisitely sensitive to MMC, whereas the mildly sensitive strain (Cockayne syndrome) overlapped with the control range. The reproducibility of the assay was evaluated within and between experiments.