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USMLE Step 1 Questions
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Genes of laterality, such as iv or inv, determine the right-left axis (“sidedness”). A mutation in a laterality gene is the most logical explanation for a child who was born with which of the following abnormalities?
Correct Answer: B. Dextrocardia
Dextrocardia (choice B) is a congenital malformation of the heart in which the heart is situated on the right side of the body. These patients require ECG leads to be placed in the reverse position. The condition is usually asymptomatic.
Bifid heart (choice A) is a congenital heart defect where the heart is split, or separated into two parts.
Double-outlet right ventricle (choice C) is a congenital heart disease where both the pulmonary artery and the aorta arise from the right ventricle.
Persistent truncus arteriosus (choice D) is a cyanotic congenital heart disease where a single arterial vessel arises from the base of the heart, and splits in to the coronary, systemic, and pulmonary arteries.
Transposition of the great vessels (choice E) is also a cyanotic congenital heart disease, where the aorta arises from the right ventricle, and the pulmonary artery from the left ventricle. The pulmonary and systemic circuits are in parallel rather than in series.
1. QuestionCategory: Genetics
Genes of laterality, such as iv or inv, determine the right-left axis (“sidedness”). A mutation in a laterality gene is the most logical explanation for a child who was born with which of the following abnormalities?Correct