In Sanger's DNA sequencing method, dideoxy ribonucleotides are used as chain terminators Because they lack:
Correct answer: B. OH group at 3rd carbon, which is required for the formation of phosphodiester bond
- A. Hydrogen at 2nd carbon, which is required for the formation of hydrogen bond
- B. OH group at 3rd carbon, which is required for the formation of phosphodiester bond
- C. Nitrogenous base at 1st carbon, which is required for the formation of hydrogen bond
- D. Phosphate group at 5th carbon, which is required for the formation of phosphodiester bond
Explanation
In Sanger's DNA sequencing method, dideoxyribonucleotides are used to terminate DNA strand elongation. The key feature of these molecules is the absence of the 3' hydroxyl (OH) group, which is essential for forming phosphodiester bonds with the next nucleotide. Without this OH group, the DNA polymerase cannot add another nucleotide, thus terminating the chain. Option B is correct as it identifies the critical role of the 3' OH group in chain elongation.Options A, C, and D describe other structural aspects that do not contribute to the chain termination process in the context of Sanger sequencing.
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