Practice Test 5 - USMLE Step 1

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. Arsenate disrupts glycolysis by substituting for phosphate in the reaction catalyzed by which of the following enzymes, leading to no net production of ATP from the pathway?
2. The patient's anemia is primarily caused by a deficiency in the production of a hormone synthesized by which of the following renal cells?
3. Based on this information, which of the following is the most appropriate conclusion?
4. The chromosomal abnormality in this man increases the risk of abnormal offspring due to the potential for producing which of the following?
5. Which of the following laboratory techniques is described in this scenario?
6. Where in the cell is the protein encoded by this mutated gene synthesized?
7. The pulmonary findings in this patient are the result of a malignancy that has a strong propensity for which type of metastatic spread?
8. The protection conferred upon the newborn is primarily mediated by which of the following mechanisms?
9. The development of this condition is caused by antibodies directed against a complex of the anticoagulant and which of the following endogenous molecules?
10. This urologic emergency is most commonly predisposed by which of the following underlying abnormalities?
11. This patient's polyuria is due to a deficiency in the secretion of a hormone from which of the following locations?
12. Deletion of which of the following genes is the most likely cause of this infant's failure to develop normal male external genitalia?
13. To analyze global mRNA expression changes in melanoma cells treated with an experimental drug, investigators isolate total RNA, reverse transcribe it to cDNA, fluorescently label the sample, and hybridize it to an array containing thousands of oligonucleotide probes spotted on a glass slide. Which laboratory technique are they using?
14. Right painful ophthalmoplegia, proptosis, V2 numbness, normal vision. Lesion?
15. Isoniazid is most likely interfering with the function of which of the following vitamins?
16. What is the name of this selective medium?
17. The fundamental principle that allows this DNA 'probe' to bind specifically to its target sequence on the chromosome is known as which of the following?
18. Administration of an intravenous bolus of nitroprusside primarily decreases afterload. Which of the following immediate changes is most likely to occur in a normal left ventricle as afterload falls?
19. This research method, which tracks the co-segregation of a genetic marker and a disease phenotype within a family, is best described as which of the following?
20. A university hospital follows a prospective cohort of 2,400 adults aged 50–75 without dementia at baseline (60% women; 30% with hypertension). Investigators test the hypothesis that chronic benzodiazepine use increases incidence of Alzheimer disease over 8 years. Exposure is defined from pharmacy refill records (≥90 days supplied per year). Annual cognitive screening and neurologist adjudication determine incident Alzheimer disease. Results: Alzheimer disease develops in 96/800 (12.0%) exposed vs 144/1,600 (9.0%) unexposed. Exposed participants have higher baseline anxiety and poorer sleep, and they attend follow-up visits less often. Investigators adjust for age, education, depression, and comorbidities, but they acknowledge persistent differences between groups. Which bias is most likely to affect the results of this study?

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