A couple are both carriers of beta-thalassemia caused by a known point mutation in the HBB gene that abolishes a restriction enzyme site. Prenatal testing is performed on fetal DNA. Which technique can directly detect this specific mutation?
- A Western blot of fetal hemoglobin
- B Karyotyping
- C PCR amplification of HBB followed by restriction digest and gel electrophoresis (RFLP) ✓
- D Northern blot for HBB mRNA
Correct answer: C. PCR amplification of HBB followed by restriction digest and gel electrophoresis (RFLP)
Explanation
RFLP detects point mutations that alter restriction sites. PCR amplifies the target region, the restriction enzyme cuts wild-type but not mutant DNA (or vice versa), and gel electrophoresis reveals different fragment sizes. Karyotyping detects only large chromosomal abnormalities. Western and Northern blots detect protein and RNA respectively, not the DNA mutation itself.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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