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Interchange trisomy 21 by t(1;21)(p22;q22)mat.
M G Dominguez1, H Rivera, A I Vasquez
1Centro Médico Nacional de Occidente, Instituto Mexicano del Seguro Social, Guadalajara, Jalisco.
Genetic Counseling (Geneva, Switzerland)
|February 12, 2002
Summary
Interchange trisomy 21, a form of Down syndrome, can arise from balanced translocations. This study analyzes cases, finding recurrence risks and abortion rates consistent with previous estimates for carrier mothers.
Area of Science:
- Genetics
- Human Genetics
- Cytogenetics
Background:
- Down syndrome is often associated with trisomy 21.
- Reciprocal translocations can lead to unbalanced segregation, resulting in conditions like interchange trisomy 21.
Observation:
- A sporadic case of interchange trisomy 21 due to t(1;21)(p22;q22)mat was identified.
- Analysis revealed translocation breakpoints primarily in chromosome 21q and involvement of larger chromosomes.
Findings:
- 3:1 segregation was the predominant mechanism, mostly involving carrier mothers.
- Recurrence risk for female carriers is estimated at 9-15%, with an abortion rate of approximately 28%.
Implications:
- Understanding translocation patterns aids in genetic counseling for families with Down syndrome.
- These findings refine recurrence risk and abortion rate estimates for carriers of interchange trisomy 21.