[Meiotic and parental origin of extra chromosome 21 in children with regular trisomy 21].
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.
Valle
Yeminia
Y
Centro de Investigación Biomédica de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco, México.
Hernández
Guillermo
G
Barajas-Barajas
Leticia Oralia
LO
Vázquez-Herrera
José Andrés
JA
Ortiz
Rocío
R
Padilla-Gutiérrez
Jorge Ramón
JR
Quintero-Ramos
Antonio
A
Rodarte
Katya
K
Olivares
Norma
N
Rivas
Fernando
F
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
D004247:DNA