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Monosomy 21: a possible stepwise evolution of the karyotype
American Journal of Medical Genetics
|January 1, 1979
Summary
This study reports a rare case of mosaic trisomy 21 in a female infant, presenting with growth and developmental issues. The findings suggest a potential explanation for previously reported "complete monosomy 21" cases.
Area of Science:
- Genetics
- Developmental Biology
- Pediatrics
Background:
- Complete monosomy for chromosome 21 (Down syndrome) is extremely rare and typically lethal.
- Understanding the genetic basis of chromosomal abnormalities is crucial for diagnosing and managing developmental disorders.
Observation:
- A female infant presented with intrauterine growth retardation, failure to thrive, craniofacial anomalies, arthrogryposis-like features, and psychomotor retardation.
- Chromosome analysis revealed mosaicism with three distinct cell lines: 45,XX,-21 / 46,XX,del(21)(q11) / 46,XX.
Findings:
- The observed mosaicism, involving different cell lines with partial or complete absence of chromosome 21, offers a novel explanation for reported cases of complete monosomy 21.
- This genetic complexity challenges traditional understandings of monosomy 21.
Implications:
- The findings highlight the importance of detailed cytogenetic analysis in cases with severe developmental abnormalities.
- Further research into chromosomal mosaicism can improve diagnostic accuracy and genetic counseling for families affected by rare chromosomal disorders.