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DNA testing for fragile X syndrome in schools for learning difficulties
S F Slaney1, A O Wilkie, M C Hirst
1Department of Medical Genetics, Churchill Hospital, Oxford.
Archives of Disease in Childhood
|January 1, 1995
Summary
Fragile X syndrome, an inherited cause of learning difficulties, was identified in four children through screening. Early diagnosis and genetic counseling are crucial for families to manage the condition and understand risks.
Area of Science:
- Genetics
- Neurodevelopmental Disorders
- Molecular Biology
Background:
- Fragile X syndrome is the leading inherited cause of intellectual disability.
- Early diagnosis is vital for patient management and identifying at-risk carriers.
- The condition involves a (CGG)n repeat expansion in the FMR1 gene at the FRAXA site (Xq27.3).
Purpose of the Study:
- To screen for Fragile X syndrome in children with unexplained moderate to severe learning difficulties.
- To assess the prevalence of undiagnosed Fragile X syndrome in this population.
- To evaluate the utility of screening and genetic counseling for affected families.
Main Methods:
- Clinical and molecular studies were conducted on 154 children.
- Southern blot analysis was used to detect the expanded (CGG)n repeat sequence in the FMR1 gene.
- Cytogenetic analysis confirmed the fragile site (FRAXA).
Main Results:
- Fragile X syndrome was diagnosed in 4 out of 154 children (2.6%).
- Affected children exhibited the characteristic large (CGG)n repeat amplification.
- Cytogenetic and further molecular studies confirmed the diagnosis.
Conclusions:
- Undiagnosed cases of Fragile X syndrome persist, highlighting diagnostic challenges.
- Screening high-risk populations may be warranted due to the implications of missed diagnoses.
- Genetic counseling and DNA testing are essential for families to determine carrier status and risks.