Medical Genetics & Genomics Command Center

In a North American Caucasian population, the incidence of cystic fibrosis (CF) is approximately 1 in 2,500 live births. A healthy man whose sister has cystic fibrosis marries a healthy woman from the general population with no family history of CF. What is the probability that their first child will be affected with cystic fibrosis?

A 2-day-old newborn experiences generalized muscle twitching and tetany. Serum calcium is 6.2 mg/dL. Physical examination reveals low-set ears, micrognathia, a cleft palate, and a harsh systolic ejection murmur over the left sternal border. An echocardiogram confirms truncus arteriosus. A microdeletion on chromosome 22q11 is suspected. Which of the following embryonic structures failed to develop properly in this infant?

A 16-year-old boy is brought for clinical evaluation due to learning difficulties and behavioral challenges. Physical examination reveals an elongated face with a prominent mandible, large protruding ears, and bilateral testicular volume exceeding 30 mL (normal < 20 mL). Genetic testing demonstrates > 250 CGG trinucleotide repeats in the 5' untranslated region of the FMR1 gene. What molecular mechanism is responsible for silencing this gene?

A biomedical researcher investigates a newly identified nuclear oncoprotein that regulates cell cycle progression by binding directly to specific enhancer DNA sequences. Which of the following laboratory techniques is best suited to demonstrate the sequence-specific DNA-binding capability of this protein?

A 38-year-old primigravida undergoes routine second-trimester quadruple screening at 16 weeks gestation. Which of the following serum marker patterns is most characteristic of a fetus with Down syndrome (Trisomy 21)?