Questões de USMLE

RNA is isolated from the rough endoplasmic reticulum of several tissues, subjected to electrophoresis, blotted, and probed with a 32P-cDNA. The results from the autoradiogram are s…

A 10-year-old female is admitted to the hospital because of a recurrent neurologic disorder. Her right arm and leg have become limp, and she is found to have lactic acidosis. Two m…

Police are investigating the case of a missing mother of 4 children. All 4 children have the same biological father. Single-locus short tandem repeat (STR) analysis was performed o…

DNA, extracted from a patient, is to be tested by PCR and DNA sequencing to ascertain the presence of a particular mutation. The DNA sequence to be amplified by PCR is shown below.…

A scientist exposes a culture of a bacterium with minimal nutritional requirements to a chemical mutagen, then streaks out the bacteria on plates filled with a complex medium suppl…

A 20-year-old male presents with progressive weakness and myotonia, most pronounced in the hands and feet. Vital signs show HR 78/min, BP 118/76 mmHg, RR 14/min. Serum creatine kin…

A 34-year-old female presents to her physician complaining of oral ulcers. A careful history reveals that she is a strict vegetarian and does not eat meat, fish, poultry, eggs, or …

A 23-year-old White female with cystic fibrosis (FEV₁ 65% predicted, pancreatic insufficiency on enzyme replacement therapy) presents with her first cousin to discuss reproductive …

A 5-year-old, intellectually impaired male is brought to the city from a rural community for evaluation. A careful history reveals intellectual impairment in a number of other fami…

A 3-week-old female infant (46, XX) presents with ambiguous genitalia, poor feeding, and lethargy. Vital signs show BP 78/52 mmHg, HR 148/min, RR 32/min, temp 36.8°C. Laboratory st…

When a cloned DNA fragment is used as a probe, a restriction fragment length polymorphism (RFLP) is revealed in the region adjacent to the centromere of chromosome 21. Four haploty…

Several members of a family have an autosomal recessive disease characterized by intellectual deterioration, weakness, ataxia, seizures, and death at a young age. Special studies f…

A 2-month-old male is evaluated for failure to thrive. As the pediatrician is examining the patient, she witnesses a seizure. Physical examination is remarkable for hepatomegaly, a…

A 2-month-old male infant presents with hypotonia, poor feeding, and seizures. Vital signs show HR 145 bpm, RR 38, BP 72/48, temperature 37.2°C, and SpO2 98% on room air. Physical …

A 52-year-old female is diagnosed with breast cancer. After discussing treatment options with her oncologist, she decides to turn to the Internet for advice. In a cancer survival c…

Genomic DNA from a child with pyruvate kinase deficiency identifies a mutation in the 3'-splice site of intron 3. The mRNA from the child's reticulocytes is used to produce cDNA. P…

A 5-day-old infant suffers a seizure and is rushed to the emergency department. The mother reports that the infant was healthy when born but has become extremely lethargic, and tha…

A 45-year-old researcher is purifying lysosomal proteins from cultured hepatocytes for functional studies. He uses affinity chromatography with a column matrix conjugated to an ant…

A 25-year-old female with type 1 diabetes mellitus has maintained good glycemic control for several years. Recently she has gained 10 pounds and joined a group exercise program. By…

Methotrexate is used as therapy for rheumatoid arthritis, but has many side effects related to competitive inhibition of the enzyme dihydrofolate reductase. These side effects can …

A 2-year-old male presents with developmental delay, hepatosplenomegaly, and progressive neurologic decline. Vital signs show HR 110 bpm, RR 24/min, BP 95/60 mmHg, and temperature …

Liver cells in culture were kept at 0°C (32.0°F) and treated with trypsin to digest the receptors on the cell surface. The temperature was then raised to 37.0°C (98.6°F), and radio…

A 45-year-old microbiologist studies a bacterial mutant with a lethal defect preventing chromosome replication. The organism shows BP 120/80, HR 78, RR 16, Temp 37°C. DNA analysis …

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 test…