Abstract | INTRODUCTION: Free trisomy 21 is responsible for 95% of Down syndrome cases. Advanced maternal age and susceptible recombination patterns are recognized risk factors associated to Down syndrome. Maternal origin of trisomy occurs in approximately 90% of cases; paternal and mitotic origin share the remaining 10%. However, the recombination events that serve as a risk factors for trisomy 21 have not been carefully characterized. OBJECTIVE: To analyze and validate observations in a sample of Colombian trysonomy 21 cases. MATERIALS AND METHODS: Twenty-two Colombian families were selected, each with one affected Down syndrome (free trisomy 21) child. Microsatellite polymorphisms were used as DNA markers to determine the parental/stage origin of non-disjunction and recombination events. Non-parametric tests were used to compare our results with those reported. Multiple correspondence analysis was used to outline different groups and their associations. RESULTS: Distribution of trisomy 21 was 90.9% maternal, 4.5% paternal and 4.5% from mitotic origin, similar to distributions reported previously. However, we found differences in the frequency of maternal meiotic stage errors between the present study (46.1% meiosis I and 53.9% meiosis II) compared to those reported previously (70% meiosis I and 30% meiosis II). Multiple correspondence analyses showed association of either local recombination events or absence of recombination with specific non-disjunction stages. CONCLUSIONS: Recombination patterns found in this study support the hypothesis that susceptible chiasmate configurations are associated to maternal meiosis I and meiosis II errors. Non-disjunction frequencies between maternal meiotic stages need to be clarified in our population.
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Authors | Nelson Javier Ramírez, Helen Marcela Belalcázar, Juan José Yunis, Luis Napoleón Quintero, Gonzalo Humberto Arboleda, Humberto Arboleda |
Journal | Biomedica : revista del Instituto Nacional de Salud
(Biomedica)
Vol. 27
Issue 1
Pg. 141-8
(Mar 2007)
ISSN: 0120-4157 [Print] Colombia |
PMID | 17546231
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Topics |
- Adolescent
- Adult
- Child
- Child, Preschool
- Chromosomes, Human, Pair 21
(genetics)
- Colombia
- Down Syndrome
(genetics)
- Female
- Humans
- Infant
- Male
- Middle Aged
- Nondisjunction, Genetic
- Parents
- Recombination, Genetic
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