A 34 year old man who received an allogeneic bone marrow transplant two years ago is arrested for a crime. His peripheral blood STR profile matches the crime scene evidence, but his buccal swab shows a completely different profile. What is the most likely explanation?
- A The crime scene evidence belongs to the bone marrow donor
- B The buccal swab was contaminated during collection
- C The transplant donor's haematopoietic DNA has repopulated his blood while his epithelial tissues retain his own genome ✓
- D He has germline chimerism involving both cell lines
Correct answer: C. The transplant donor's haematopoietic DNA has repopulated his blood while his epithelial tissues retain his own genome
Explanation
After allogeneic bone marrow transplantation, circulating leukocytes carry the donor's DNA, so blood based STR profiling reflects the donor genotype. Epithelial cells lining the buccal mucosa are not replaced by the graft and still yield the recipient's authentic profile. For reference sampling in such individuals, a buccal or other epithelial sample must be used, and the analyst must know the transplant history to avoid a false attribution.
Reference: Butler, Forensic DNA Typing, 2nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.