## **Core Concept**
DNA (Deoxyribonucleic acid) is a polymer composed of nucleotides. Each nucleotide is made up of a nitrogenous base, a sugar molecule called deoxyribose, and a phosphate group. On complete hydrolysis, DNA breaks down into its basic components.

## **Why the Correct Answer is Right**
Complete hydrolysis of DNA yields its basic building blocks: the phosphate group, the sugar deoxyribose, and the nitrogenous bases. The nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). Uracil is not a component of DNA; it is found in RNA (ribonucleic acid) instead, where it replaces thymine.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Phosphate group - This is a correct component of DNA and is released on hydrolysis.
- **Option B:** Deoxyribose - This is the sugar component of DNA and is also released on hydrolysis.
- **Option C:** Adenine - This is one of the nitrogenous bases in DNA, making it a correct component.

## **Why Option D is Correct (and thus the question's "except")**
- **Option D:** Uracil - This is incorrect in the context of DNA components. Uracil is a nitrogenous base found in RNA, not DNA.

## **Clinical Pearl / High-Yield Fact**
Remembering the basic composition of DNA and RNA can be crucial for various biochemical and molecular biology questions. A simple way to recall the difference is: DNA contains **T**hymine, while RNA contains **U**racil.

## **Correct Answer:** . Uracil