Molecular Biology/Genetics USMLE Step 1 Practice Question
A 24-year-old female with phenylketonuria (PKU) gives birth to her first child. Although there is no history of PKU in the father's family, the couple could not afford genetic testing of the father or consistent prenatal care. At birth, the child is small, microcephalic, and has elevated blood phenylalanine. What is the most likely explanation for this neonate's symptoms?
Answer choices
- AFather is a carrier of PKU
- BMaternal uniparental disomy
- CMaternal translocation with unbalanced segregation in meiosis I
- DMaternal translocation with unbalanced segregation in meiosis II
- EPhenylalanine was not adequately restricted from the mother's diet during pregnancyCorrect answer
- FThe child inherited two mutant alleles from the heterozygous father
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.