title: [Meiotic and parental origin of extra chromosome 21 in children with regular trisomy 21].
abstract: BACKGROUND
  Down syndrome (DS) or trisomy 21 is the most common chromosomal abnormality in live birth children. Most cases are regular trisomies 21 secondary to a maternal non-disjunction (ND). Meiotic and parental origins have been recently investigated by segregating genetic markers from DNA hypervariable regions.
  
  
  OBJECTIVE
  To identify the meiotic and parental origin in children with regular trisomy 21.
  
  
  METHODS
  There were analyze 20 groups of three (every group included parents and child with Down syndrome). There were used soothe following markers: D21S11, D21S1260, and D21S265.
  
  
  RESULTS
  The ND occurred during the first meiotic division (M1) in 13 cases and at the second meiotic division (M2) in the other seven. Twelve out of the 13 NDs from the first group were maternal and one paternal. The parental origin within the M2 group was not elucidated.
  
  
  CONCLUSIONS
  Meiotic origin was identified in all cases. As in other reports, the origin of trisomy 21 in the present population is mainly secondary to a maternal ND in M1.
authors.affiliation: Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México.
authors.forename: Yeminia
authors.initials: Y
authors.lastname: Valle
authors.forename: Guillermo
authors.initials: G
authors.lastname: Hernández
authors.forename: Leticia Oralia
authors.initials: LO
authors.lastname: Barajas-Barajas
authors.forename: José Andrés
authors.initials: JA
authors.lastname: Vázquez-Herrera
authors.forename: Rocío
authors.initials: R
authors.lastname: Ortiz
authors.forename: Jorge Ramón
authors.initials: JR
authors.lastname: Padilla-Gutiérrez
authors.forename: Antonio
authors.initials: A
authors.lastname: Quintero-Ramos
authors.forename: Katya
authors.initials: K
authors.lastname: Rodarte
authors.forename: Norma
authors.initials: N
authors.lastname: Olivares
authors.forename: Fernando
authors.initials: F
authors.lastname: Rivas
mesh_terms: D002648:Child; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics; D004247:DNA / Q000032:analysis; D004314:Down Syndrome / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008540:Meiosis / Q000235:genetics; D010290:Parents; D016133:Polymerase Chain Reaction
chemical_list: D004247:DNA