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Non-disjunction of chromosome 18
M Bugge1, A Collins, M B Petersen
1The John F.Kennedy Institute, Glostrup, Denmark. mb@biokemi.imbg.ku.dk
Human Molecular Genetics
|May 16, 1998
Summary
Maternal meiosis II errors most frequently cause trisomy 18, differing from other trisomies. Chromosome-specific factors influence non-disjunction, challenging simple models of recombination and meiotic errors.
Area of Science:
- Genetics
- Cell Biology
- Reproductive Biology
Background:
- Trisomy 18 (Edwards syndrome) is a common chromosomal abnormality.
- Most human trisomies result from maternal meiosis I errors.
- The specific mechanisms causing trisomy 18 non-disjunction are not fully understood.
Purpose of the Study:
- To determine the primary cause of maternal non-disjunction for chromosome 18.
- To investigate the role of recombination and chiasma distribution in trisomy 18.
- To compare trisomy 18 mechanisms with other human trisomies.
Main Methods:
- Analysis of 100 trisomy 18 conceptuses.
- Comparison with a published dataset of 61 conceptuses.
- Examination of recombination frequencies and chiasma distributions in maternal meiosis I and II.
Main Results:
- Maternal meiosis II errors are the most frequent cause of trisomy 18 non-disjunction.
- Unlike other trisomies, maternal meiosis I non-disjunction in trisomy 18 shows specific recombination patterns.
- Maternal meiosis II non-disjunction in trisomy 18 does not align with the entanglement model, showing reduced recombination.
- Nullichiasmate tetrads are observed in maternal meiosis I non-disjunction but not in meiosis II non-disjunction for chromosome 18.
Conclusions:
- Maternal meiosis II errors are the predominant cause of trisomy 18.
- Chromosome-specific factors significantly influence meiotic non-disjunction.
- Existing models of recombination and meiotic errors require refinement to account for chromosome-specific variations.