title: Parental origin and mechanism of formation of X chromosome structural abnormalities: four cases determined with RFLPs.
abstract: Parental origin and mechanism of formation of X chromosome structural abnormalities were studied in one each case of dup(X)(pter----p11.4::p22.1----qter), del(X)(qter----p11:), i(X)(qter----cen----qter), and inv dup(X) (pter----q22::q22----pter) using various X-linked RFLPs as genetic markers. Segregation and densitometric analyses on polymorphic DNAs revealed that the dup(Xp) and the del(Xp) are both of paternal origin and the i(Xq) and i dic(X) are of maternal origin. The dup(Xp) had arisen by an unequal sister chromatid exchange and the del(Xp) had occurred through an intrachromosomal breakage-reunion mechanism, both in the paternal X chromosome. The i(Xq) had arisen either through centromere fission of a maternal X chromosome, followed by duplication of its long-arm, or through a translocation between two maternal X chromosomes after meiotic crossing-over. The inv dup(X) arose through sister chromatid breakage and reunion in a maternal X chromosome. These results, together with those of previous studies, suggest that the de novo abnormalities due to events involving centromere disruption arise predominantly during oogenesis, while those due to simple breakage-reunion events occur preferentially during spermatogenesis.
authors.affiliation: Department of Human Genetics, Nagasaki University School of Medicine, Japan.
authors.forename: H X
authors.initials: HX
authors.lastname: Deng
authors.forename: J H
authors.initials: JH
authors.lastname: Xia
authors.forename: M
authors.initials: M
authors.lastname: Ishikawa
authors.forename: N
authors.initials: N
authors.lastname: Niikawa
mesh_terms: D002675:Child, Preschool; D005260:Female; D008040:Genetic Linkage; D005819:Genetic Markers; D006801:Humans; D010290:Parents; D012150:Polymorphism, Restriction Fragment Length; D012729:Sex Chromosome Aberrations / Q000235:genetics*; D014960:X Chromosome
chemical_list: D005819:Genetic Markers