A 6-Year-Old Boy Is Brought to the Office Due to a Persistent

question 67

Multiple Choice

A 6-year-old boy is brought to the office due to a persistent facial ulcer for the past 2 months.  His mother reports that the patient has extreme sensitivity to sunlight and has developed freckles on his face, neck, and limbs since infancy.  On physical examination, the skin in sun-exposed areas is dry and rough with numerous freckles and erythematous macules.  There is an ulcerated plaque on the left face; a biopsy reveals squamous cell carcinoma.  Further testing leads to a diagnosis of xeroderma pigmentosum.  A defect in which of the following enzymes is most likely causing this patient's condition?

• A)3'→5' exonuclease
• B)DNA ligase
• C)Endonuclease
• D)Helicase
• E)Topoisomerase

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Definitions:

Stereotyping

The act of assigning oversimplified or generalized traits, behaviors, or beliefs to a particular group of people without acknowledging individual variation.

Case Study

A research method that involves an in-depth analysis of a single individual, event, or group to explore causation in order to find underlying principles.

Heating System

A mechanism in buildings used to maintain a comfortable temperature by generating and distributing heat.

Qualities

Distinctive characteristics or attributes of a person or thing that define their nature or behavior.