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:

Defense Mechanisms

Psychological strategies brought into play by individuals to handle reality and maintain self-image by protecting themselves from unpleasant emotions like guilt and anxiety.

Repression

A defense mechanism in psychoanalytic theory where unpleasant thoughts, feelings, or memories are unconsciously excluded from consciousness.

Psychological

Relating to the mind or mental processes and how these affect behavior and well-being.

Freud's Psychosexual

A theory proposed by Sigmund Freud that describes how personality develops early in life from childhood through several psychosexual stages.