Practice Exam-Clinical Molecular Genetics

Clinical Molecular Genetics

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The document features questions related to Clinical Molecular Genetics as part of a practice exam by Claudia Barnett. <br /><br />**Question ID 25223**:<br />The focus is on interpreting a Southern blot result to identify patients at risk of developing Premature Ovarian Insufficiency (POI) in the context of Fragile X syndrome. Key details provided include:<br /><br />- **Patient B**: Identified as a female premutation carrier, characterized by four bands indicating both normal CGG repeats and expanded premutation CGG repeats. Premutation carriers of Fragile X are at risk for POI.<br />- **Patient A**: Male with full mutation.<br />- **Patient C**: Male with premutation.<br />- **Patient D**: Normal female.<br />- **Patient E**: Female with full mutation.<br />- **Patient F**: Normal male.<br /><br />Thus, patients at risk for POI would involve Patient B, leading to Option C being correct, highlighting the sensitivity of premutation carriers to POI.<br /><br />**Question ID 25222**:<br />Addresses carrier screening for spinal muscular atrophy (SMA). Pertinent information includes:<br /><br />- 6-8% of parents of a child with SMA might show normal SMN1 dosage testing.<br />- 4-6% of carriers may possess two SMN1 copies on a single chromosome. De novo mutations occur in 2-4% of cases.<br />- The haplotype associated with silent carrier status increases among Ashkenazi Jewish individuals.<br />- A duplication of the SMN1 gene on one chromosome alongside deletion on another occurs in 5-8% of the population.<br /><br />This context implies Option C is considered accurate regarding the presence of a modifier variant linked to silent carriers.<br /><br />These answers and details within the questions stress the complexities of genetic testing and carrier screening for hereditary conditions.

Keywords

Clinical Molecular Genetics

Southern blot

Premature Ovarian Insufficiency

Fragile X syndrome

premutation carrier

spinal muscular atrophy

SMN1 gene

carrier screening

genetic testing

hereditary conditions