A 5-year-old boy presents with spontaneous joint bleeding and easy bruising. Laboratory tests show prolonged activated partial thromboplastin time (aPTT) and low factor VIII levels.  What is the most likely diagnosis? 

A 35-year-old female is diagnosed with melanoma. Genetic testing reveals a gain-of-function mutation in the BRAF gene, a proto-oncogene.  What is the primary consequence of this mutation? 

What is the primary structural difference between hemoglobin A and hemoglobin S? 

A 50-year-old male presents with numbness and tingling in his ring and little fingers. He reports that his symptoms are worse when he leans on his elbow or bends his arm for extended periods. Physical examination reveals a positive Tinel’s sign at the elbow.  What is the most likely diagnosis? 

A patient who recovered from a previous infection has a rapid and robust immune response upon re-exposure to the same pathogen. Which cells are responsible for this enhanced response in humoral immunity? 

A 50-year-old male with a history of hepatitis B infection is diagnosed with liver cancer.   How can hepatitis B virus contribute to cancer development? 

A patient is infected with a bacterial pathogen. Which cells present antigens to CD4 T cells to initiate an adaptive immune response? 

A 55-year-old female with breast cancer is found to have cells that have undergone epithelial–mesenchymal transition (EMT).  What is the primary consequence of EMT in cancer progression? 

Where do B cells develop and mature? 

A newborn presents with asymmetry in gluteal folds during a well-baby exam. The Ortolani maneuver elicits a palpable “clunk.” Which of the following is the most likely diagnosis?