A 5-month-old male infant from a consanguineous marriage presents with severe sunburns and freckling in sun exposed areas. The mother explains that the infant experiences these sunburns every time the infant goes outside despite applying copious amounts of sunscreen. Which of the following DNA repair mechanisms is defective in this child?
ANon-homologous end joining
BHomologous recombination
CBase excision repair
DMismatch repair
ENucleotide excision repair
An investigator is studying the normal process of shrinking of the thymus gland with increasing age in humans. Thymic size is found to gradually start decreasing during puberty. Which of the following enzymes is most likely involved in the process underlying the decline in thymus mass with aging?
ALipase
BCollagenase
CMetalloproteinase
DCaspase
ENADPH oxidase
A 17-year-old patient presents to the emergency department with left wrist pain after falling off of his bike and landing on his left hand. On physical exam the thenar eminence is red, swollen, and tender to palpation, so a radiograph is ordered. The patient is worried because he learned in biology class that radiography can cause cancer through damaging DNA but the physician reassures him that radiographs give a very minor dose of radiation. What is the most common mechanism by which ionizing radiation damages DNA?
AStrand breakage
BThymidine dimer formation
CMicrosatellite instability
DCyclobutane pyrimidine dimer formation
ECytosine deamination
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