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

Options

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

Answer

To solve the question regarding the prevention of polymerization of nucleotides in DNA, we can follow these steps:

### Step 1: Understand the Structure of DNA
DNA is composed of nucleotides, which are the building blocks. Each nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (either a purine or a pyrimidine). The nucleotides are linked together by phosphodiester bonds between the 3' hydroxyl (OH) group of one nucleotide and the 5' phosphate group of the next nucleotide.

**Hint:** Recall that the structure of DNA includes the 3' and 5' ends, which are crucial for understanding how nucleotides link together.

### Step 2: Identify the Role of the 3' OH Group
The polymerization of nucleotides occurs when the 3' OH group of one nucleotide reacts with the 5' phosphate of another nucleotide, forming a phosphodiester bond. This is essential for the elongation of the DNA strand.

**Hint:** Focus on the functional groups involved in the bonding process. The 3' OH group is key to forming the link between nucleotides.

### Step 3: Analyze the Options Provided
The question provides several options to prevent polymerization:
- A) Replace purines with pyrimidines
- B) Remove or replace the 3' OH group in deoxyribose
- C) Remove or replace the 2' OH group with some other group in deoxyribose
- D) Both B and C

To prevent polymerization, we need to target the 3' OH group, as it is directly involved in forming the phosphodiester bond.

**Hint:** Consider which modifications would directly affect the ability of nucleotides to link together.

### Step 4: Determine the Correct Modification
Among the options, option B (removing or replacing the 3' OH group in deoxyribose) directly prevents the formation of phosphodiester bonds, thereby stopping polymerization. Option C does not directly affect the polymerization process, as the 2' OH group is not involved in the bond formation between nucleotides.

**Hint:** Think about which modification would most effectively disrupt the bonding process.

### Step 5: Conclusion
The best choice to prevent the polymerization of nucleotides in DNA is to **remove or replace the 3' OH group in deoxyribose** (option B).

**Final Answer:** B) Remove or replace the 3' OH group in deoxyribose.