title: Isodicentric Y chromosomes and secondary microchromosomes.
abstract: We report here on two mosaic patients with both an idic(Yp) and a microchromosome. FISH with the DYZ3 alphoid repeat demonstrated that the isodicentrics effectively exhibited two alphoid clusters whereas the small markers had a Y-centromere. These data, along with 4 previous observations, indicate that such microchromosomes effectively result from functional dicentricity of isodicentric Y-chromosomes and represent the excision of one centromere plus various amounts of adjacent chromatin. Other than a real infrequency of such a concurrence or a very low proportion of the cell line(s) containing the microchromosome, the paucity of observations points to a high rate of underdiagnosis as revealed by two idic(Y) instances in which the microchromosome was detected only in samples assessed by FISH.
authors.affiliation: División de Genética, Instituto Mexicano del Seguro Social, Guadalajara, Jal., Mexico. hrivera@cencar.udg.mx
authors.forename: H
authors.initials: H
authors.lastname: Rivera
authors.forename: L M
authors.initials: LM
authors.lastname: Ayala-Madrigal
authors.forename: M
authors.initials: M
authors.lastname: Gutiérrez-Angulo
authors.forename: A I
authors.initials: AI
authors.lastname: Vasquez
authors.forename: A L
authors.initials: AL
authors.lastname: Ramos
mesh_terms: D041322:Chromosomes, Human, Y / Q000235:genetics*; D003937:Diagnosis, Differential; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008677:Metaphase / Q000235:genetics; D009030:Mosaicism / Q000235:genetics*; D014424:Turner Syndrome / Q000235:genetics*