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Parental origin of autosomal trisomies
Annals of Human Genetics
|May 1, 1984
Summary
Maternal meiosis I non-disjunction is the primary cause of trisomy in spontaneous abortions. However, trisomy 21 shows a higher paternal origin, linked to an excess of males, unlike other autosomal trisomies.
Area of Science:
- Human Genetics
- Reproductive Biology
- Cytogenetics
Background:
- Autosomal trisomies are common causes of spontaneous abortions.
- Understanding the parental origin of trisomy is crucial for genetic counseling and reproductive health.
- Previous studies suggest maternal meiotic errors are the predominant source of trisomy.
Purpose of the Study:
- To determine the parental origin of 204 cases of spontaneous abortions with single trisomies, mosaic trisomies, and double trisomies.
- To investigate the influence of maternal age on the origin of trisomy.
- To compare the origin of trisomy 21 with other autosomal trisomies and explore potential sex-specific mechanisms.
Main Methods:
- Comparative analysis of chromosome heteromorphisms between parents and their trisomic spontaneous abortions.
- Categorization of trisomies by chromosome number, including trisomy 3, 4, 9, 13, 14, 15, 16, 21, and 22.
- Statistical analysis to determine the most likely source of non-disjunction (maternal meiosis I, maternal meiosis II, or paternal meiosis).
Main Results:
- Maternal meiosis I non-disjunction was identified as the most frequent cause of trisomy across all studied cases, including mosaics, irrespective of maternal age.
- Trisomy 21 exhibited a significantly higher proportion of paternally derived cases compared to all other autosomal trisomies.
- Cases of trisomy 21 with paternal origin showed an excess of males, suggesting a link between paternal first meiotic division non-disjunction and male excess in this specific trisomy.
Conclusions:
- Maternal meiosis I errors are the primary mechanism leading to autosomal trisomies in spontaneous abortions.
- Trisomy 21 represents a distinct category due to its increased paternal origin and association with male excess, likely due to paternal meiotic errors.
- These findings have implications for understanding the etiology of specific chromosomal abnormalities and may inform genetic counseling regarding recurrence risks.