Fanconi anemia

A 16-month-old boy is brought by his parents to the pediatrician’s office to establish care. The patient’s family recently immigrated from Eastern Europe, and medical records are not available. The mother notes that the patient has not been growing as quickly as his siblings grew. In the office, the patient’s temperature is 37.5°C (99.5°F), blood pressure is 105/62 mmHg, pulse is 100/min, and respirations are 28/min. Physical exam reveals hyperpigmented spots on the patient’s body and hypoplastic thumbs. The patient’s height, weight, and head circumference are below the 3rd percentile. Laboratory testing reveals the following results:  
 

Laboratory value	Result
Hemoglobin	8.1 g/dL
Leukocyte	2,300/mm3
Platelet	65,000/mm3
Mean Corpuscular Volume	109 mm3

The patient’s condition is most likely due to a defect involving which of the following processes?