The fundamental principle of Sanger dideoxy chain termination sequencing is that:
- A Ribonucleotides are randomly incorporated, stalling elongation at defined positions
- B Dideoxynucleotides lacking the 3' hydroxyl group are incorporated, terminating strand extension when inserted ✓
- C Restriction enzymes cut amplified DNA into fragments whose sizes reveal the sequence
- D Fluorescent probes hybridise to complementary sequences and are read directly by laser scanning
Correct answer: B. Dideoxynucleotides lacking the 3' hydroxyl group are incorporated, terminating strand extension when inserted
Explanation
Sanger sequencing relies on incorporation of dideoxynucleotide triphosphates that lack the 3' OH group, so once one is added no further phosphodiester bond can form and the chain terminates at that base. Fluorescently labelled ddNTPs generate fragments of every possible length, resolved by capillary electrophoresis. Hybridisation-based reading describes microarrays, not Sanger sequencing.
Reference: Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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