ORIGINAL ARTICLE |
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Year : 2012 | Volume
: 18
| Issue : 2 | Page : 204-216 |
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Discerning non-disjunction in down syndrome patients by means of GluK1-(AGAT) n and D21S2055-(GATA) n microsatellites on chromosome 21
Ghosh Debarati1, Sinha Swagata2, Chatterjee Anindita2, Nandagopal Krishnadas1
1 Manovikas Biomedical Research & Diagnostic Centre; Manovikas Kendra Rehabilitation & Research Institute for the Handicapped, 482 Madudah, Plot I-24, Sector-J, Eastern Metropolitan Bypass, Kolkata, India 2 Manovikas Kendra Rehabilitation & Research Institute for the Handicapped, 482 Madudah, Plot I-24, Sector-J, Eastern Metropolitan Bypass, Kolkata, India
Correspondence Address:
Nandagopal Krishnadas Manovikas Biomedical Research & Diagnostic Centre, Manovikas Kendra Rehabilitation & Research Institute for the Handicapped, 482 Madudah, Plot I-24, Sector-J, Eastern Metropolitan Bypass, Kolkata-700107 India
Source of Support: None, Conflict of Interest: None | 3 |
DOI: 10.4103/0971-6866.100769
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Introduction: Down syndrome (DS), the leading genetic cause of mental retardation, stems from non-disjunction of chromosome 21.
Aim: Our aim was to discern non-disjunction in DS patients by genotyping GluK1-(AGAT) n and D21S2055-(GATA) n microsatellites on chromosome 21 using a family-based study design.
Materials and Methods: We have used a PCR and automated DNA sequencing followed by appropriate statistical analysis of genotype data for the present study
Results and Discussion: We show that a high power of discrimination and a low probability of matching indicate that both markers may be used to distinguish between two unrelated individuals. That the D21S2055-(GATA) n allele distribution is evenly balanced, is indicated by a high power of exclusion [PE=0.280]. The estimated values of observed heterozygosity and polymorphism information content reveal that relative to GluK1-(AGAT) n [H obs =0.286], the D21S2055- (GATA) n [H obs =0.791] marker, is more informative. Though allele frequencies for both polymorphisms do not conform to Hardy-Weinberg equilibrium proportions, we were able to discern the parental origin of non-disjunction and also garnered evidence for triallelic (1:1:1) inheritance. The estimated proportion of meiosis-I to meiosis-II errors is 2:1 in maternal and 4:1 in paternal cases for GluK1-(AGAT) n , whereas for D21S2055-(GATA) n , the ratio is 2:1 in both maternal and paternal cases. Results underscore a need to systematically evaluate additional chromosome 21-specific markers in the context of non-disjunction DS. |
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