## Why option 3 is correct The structure marked **A** — Robertsonian translocation t(13;14) — represents fusion of two acrocentric chromosomes at their centromeres, resulting in loss of short arms (containing mostly non-essential rRNA genes). Although the patient is phenotypically normal (balanced carrier with 45 chromosomes but no missing essential genetic material), meiosis in a carrier produces unbalanced gametes at significant frequency, leading to trisomy 13, monosomy 13/14 (usually lethal), or normal/balanced offspring. The two miscarriages are consistent with unbalanced conceptuses. The appropriate management is to counsel the couple about reproductive risks, offer prenatal diagnosis (karyotype and chromosomal microarray ± FISH) in future pregnancies to detect unbalanced fetuses, or pursue preimplantation genetic testing for aneuploidy (PGD-A) in IVF to select euploid embryos. This approach is evidence-based and aligns with Harrison 21e and international genetic counseling guidelines for Robertsonian translocation carriers. ## Why each distractor is wrong - **Option 1**: Dangerously misleading. The translocation directly explains the recurrent miscarriage pattern; reassurance without counseling about reproductive risk and diagnostic options abandons the patient and ignores the established link between balanced Robertsonian carriers and increased aneuploidy risk in offspring. - **Option 2**: Incorrect and overly pessimistic. The patient is a balanced carrier, not a 21;21 homozygote (which would result in ~100% trisomy 21 offspring). t(13;14) carriers have a significant but not absolute risk of unbalanced offspring; many pregnancies result in normal or balanced karyotypes. Recommending adoption or donor gametes without discussing prenatal diagnosis or PGD is premature and not standard of care. - **Option 4**: Misguided. While cascade family testing of relatives may be offered for reproductive planning, it is NOT the immediate next step for this couple. The priority is counseling the patient and her partner about their own reproductive risks and offering prenatal or preimplantation diagnostic options. Testing parents/siblings does not change management of the current couple's pregnancy planning. **High-Yield:** Balanced Robertsonian translocation carriers are phenotypically normal but produce unbalanced gametes → recurrent miscarriage or affected offspring; counsel about prenatal diagnosis (karyotype/microarray) or PGD-A in IVF. [cite: Harrison 21e Ch 471; Genetics of Chromosomal Abnormalities]
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