question: Q:A 5-year-old girl is brought to the physician by her mother for a 6-week history of fatigue, fever, and recurrent epistaxis. She has a history of duodenal atresia and an atrioventricular septal defect. She is at the 5th percentile for height and 30th percentile for weight. Physical examination shows painless cervical lymphadenopathy. Her hands are short and broad and there is a space between the first and second toes bilaterally. The spleen tip is palpated 3 cm below the left costal margin. Bone marrow aspirate shows leukocytosis with 50% lymphoblasts. Which of the following best explains this patient's condition?? 
  {'A': 'Meiotic nondisjunction', 'B': 'Deletion of a chromosome segment', 'C': 'Uniparental disomy', 'D': 'Trinucleotide repeat expansion', 'E': 'Unbalanced Robertsonian translocation'},