A family pedigree reveals first- and second-generation female relatives with premature menopause and male relatives with a progressive neurodegenerative disorder starting by their sixth decade. There are more males than females exhibiting mental retardation from childhood by the fourth generation. Genetic analysis of affected persons reveals CGG repeat expansions in a gene encoding for a protein that binds mRNA transcripts in neurons and shuttles them to the synapses. An abnormality involving which of the following organs is most likely to be present in affected males?
A family pedigree reveals first- and second-generation female relatives with premature menopause and male relatives with a progressive neurodegenerative disorder starting by their sixth decade. There are more males than females exhibiting mental retardation from childhood by the fourth generation. Genetic analysis of affected persons reveals CGG repeat expansions in a gene encoding for a protein that binds mRNA transcripts in neurons and shuttles them to the synapses. An abnormality involving which of the following organs is most likely to be present in affected males?
💡 Explanation
## **Core Concept**
The question describes a genetic disorder characterized by CGG repeat expansions in a gene encoding a protein involved in mRNA transport in neurons. This condition affects multiple generations with varied symptoms across genders, suggesting an X-linked inheritance pattern. The disorder described aligns with Fragile X Syndrome (FXS), which results from an expansion of CGG repeats in the FMR1 gene.
## **Why the Correct Answer is Right**
The correct answer, , relates to the testis. Fragile X Syndrome is caused by an expansion of CGG repeats in the FMR1 gene, leading to the absence or deficiency of the fragile X mental retardation protein (FMRP). FMRP binds mRNA transcripts in neurons and is crucial for transporting these transcripts to synapses, affecting neuronal function and development. Males are more frequently and severely affected than females due to having only one X chromosome. One of the physical features in post-pubertal males with FXS can be macroorchidism (enlarged testicles), which is a key clinical finding.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, although the heart can have issues in various genetic syndromes, it is not specifically associated with the primary features of Fragile X Syndrome.
- **Option B:** This option is incorrect as there is no direct, commonly recognized association between Fragile X Syndrome and abnormalities of the liver as a primary feature.
- **Option C:** This option is incorrect because, while cognitive and psychiatric issues are prominent in FXS, the question seems to point towards a more physically identifiable organ abnormality.
- **Option D:** This option is incorrect as it does not directly relate to a commonly identified feature of Fragile X Syndrome.
## **Clinical Pearl / High-Yield Fact**
A key clinical feature of Fragile X Syndrome in post-pubertal males is **macroorchidism** (enlarged testicles), which is a significant and distinctive physical finding. This condition often presents with developmental delays, intellectual disability, and characteristic physical features, along with a variety of behavioral and medical issues.
## **Correct Answer: D. Testis**
✓ Correct Answer: D. Testis
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