Which of the following bond is not present in DNA ?

Options

A. `beta`- 1- 9 - N- glycoside bond
B. `3-5` phosphodiester bond
C. `beta- 1-1-N` glycosidic bond
D. `beta - 1-2- N` - glycosidic bond

Answer

To determine which bond is not present in DNA, we need to analyze the types of bonds that are typically found in its structure. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the Types of Bonds in DNA
DNA is composed of nucleotides, which are the building blocks of DNA. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. The bonds present in DNA include:
- **Hydrogen Bonds**: These are found between the nitrogenous bases of the two strands of DNA, holding the strands together.
- **Glycosidic Bonds**: These connect the sugar molecule to the nitrogenous base in each nucleotide.
- **Phosphodiester Bonds**: These link the phosphate group of one nucleotide to the sugar of the next nucleotide, forming the backbone of the DNA strand.

### Step 2: Analyze the Options Given
The question provides several options regarding different types of bonds. We need to evaluate each option:
1. **Beta 1-9 Glycosidic Bond**: This bond connects the sugar to the nitrogenous base and is present in DNA.
2. **3-5 Phosphodiester Bond**: This bond is also present in DNA, linking nucleotides together.
3. **Beta 1-1 Glycosidic Bond**: This bond is not a standard bond found in DNA.
4. **Beta 1-2 Glycosidic Bond**: This bond does not exist in the context of DNA structure.

### Step 3: Conclusion
After analyzing the options, we find that the **Beta 1-2 Glycosidic Bond** is not present in DNA. Therefore, the answer to the question is that the bond which is not present in DNA is the **Beta 1-2 Glycosidic Bond**.

### Summary of the Answer
The bond that is not present in DNA is the **Beta 1-2 Glycosidic Bond**.

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