title: Determining the origin of human X isochromosomes by use of DNA sequence polymorphisms and detection of an apparent i(Xq) with Xp sequences.
abstract: The parental origin of five X isochromosomes were determined using 11 DNA markers. The isochromosome was derived from a maternal X chromosome in three cases and from a paternal X chromosome in two. Unexpected heterozygosity was detected for the proximal Xp region in one individual in whom the i(Xq) chromosome was paternally derived. This was confirmed by in situ hybridisation. A mode of formation of isochromosomes by breakage and reunion between the sister chromatids of the arms of an X chromosome is proposed to account for this. Sister chromatid breakage and reunion can be considered as a significant mechanism for the origin of i(Xq) chromosomes.
mesh_terms: D002869:Chromosome Aberrations; D002871:Chromosome Banding; D004247:DNA / Q000235:genetics*; D005260:Female; D005819:Genetic Markers; D006801:Humans; D007621:Karyotyping; D008297:Male; D008540:Meiosis; D008957:Models, Genetic; D009693:Nucleic Acid Hybridization; D011110:Polymorphism, Genetic; D014424:Turner Syndrome / Q000235:genetics*; D014960:X Chromosome
chemical_list: D005819:Genetic Markers; D004247:DNA