Glycosidic bond exists in DNA molecule between

(A) Sugar and phosphate

(B) Any two nitrogen bases

(C) Sugar and a nitrogen base

(D) Purines and pyrimidines

The correct answer to your question is (C) Sugar and a nitrogen base. In the structure of DNA, glycosidic bonds play a crucial role in linking the sugar component of the nucleotide to its corresponding nitrogenous base. Let’s break this down further to understand why this is the case.

Understanding the Structure of DNA

DNA, or deoxyribonucleic acid, is composed of long chains of nucleotides. Each nucleotide consists of three components:

• A phosphate group
• A sugar molecule (specifically deoxyribose in DNA)
• A nitrogenous base (which can be adenine, thymine, cytosine, or guanine)

The Role of Glycosidic Bonds

The glycosidic bond specifically refers to the connection formed between the sugar and the nitrogenous base. This bond is crucial because it helps to form the backbone of the DNA strand. Here’s how it works:

• The sugar molecule has a hydroxyl group (-OH) that reacts with the nitrogen atom of the nitrogenous base.
• This reaction results in the formation of a covalent bond, which is the glycosidic bond.
• As a result, each nucleotide is formed by attaching a nitrogenous base to a sugar, creating a stable structure that can be linked to other nucleotides through phosphate groups.

Why Other Options Are Incorrect

Let’s briefly examine why the other options do not represent the correct relationship:

• (A) Sugar and phosphate: This connection is known as a phosphodiester bond, not a glycosidic bond. It links the phosphate of one nucleotide to the sugar of another, forming the DNA backbone.
• (B) Any two nitrogen bases: While nitrogen bases pair with each other (adenine with thymine and cytosine with guanine) through hydrogen bonds, they do not form glycosidic bonds.
• (D) Purines and pyrimidines: This term refers to the classification of nitrogenous bases (purines are adenine and guanine, while pyrimidines are cytosine and thymine). They pair through hydrogen bonds, but again, this does not involve glycosidic bonds.

Conclusion

In summary, the glycosidic bond is specifically the connection between the sugar and the nitrogen base in a nucleotide. This bond is essential for the integrity and structure of DNA, allowing it to carry genetic information effectively. Understanding these bonds and their roles helps clarify how DNA functions at a molecular level.