Question

DNA is a polymer of nucleotides which are linked to each other by 3’-5’ phosphodiester bonds. To prevent polymerisation of nucleotides, which of the following modifications would you choose?

• A. Remove/ Replace 3' OH group in deoxyribose
• B. Both ‘b’ and ‘c’
• C. Replace purine with pyrimidines
• D. Remove/ Replace 2' OH group with some other group in deoxy ribose

Answer 1

The correct option is A Remove/ Replace 3' OH group in deoxyribose

Polymerisation of nucleotides:

Nucleotides are joined together by a condensation reaction that releases a pyrophosphate molecule and results in the formation of phosphodiester bonds. This process is called the polymerisation of nucleotides to form a DNA molecule.


Phosphodiester bond:

In a DNA strand, nucleotides are linked together by phosphodiester bonds. The 3’ - OH of one nucleotide forms a phosphodiester bond with the 5’- phosphate group of another nucleotide.


Replace purine with pyrimidines:

In the structure of DNA, both purines and pyrimidines are used for polymerisation. Hence replacing purines with pyrimidines or vice versa will not stop the polymerization of nucleotides.


Remove/ Replace 3' OH group in deoxyribose:

DNA polymerase adds new nucleotides on the 3'- OH position of the previous nucleotide by a nucleophilic attack. Therefore by removing 3'-OH, polymerization of nucleotides can be prevented.


Remove/ Replace 2' OH group:

In DNA structure, deoxyribonucleotides (dNTPs) are used for polymerisation. These dNTPs lack the 2'- OH group. They have only 2'-H groups.

Thus, one cannot remove the 2'-OH group from dNTPs.





Final answer: b. Remove/Replace 3' OH group in deoxyribose