Find the correct statement regarding DNA.

Options

A. Form a double helical structure made up of two polypeptide chain.
B. It is an acidic substance present in nucleus was first identified by F. Meischer in 1869.
C. Phosphate group is linked to 5' H of the nucleoside byglycosidic linkage .
D. All four deoxyribonucleotides are always equally present in the strands .

Answer

To solve the question regarding the correct statement about DNA, we will analyze each statement provided and determine its accuracy.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "The double helical structure is made up of two polypeptide chains."
- **Analysis**: This statement is incorrect. DNA is composed of two strands of polynucleotides, not polypeptides. Polypeptides are chains of amino acids that make up proteins, while DNA is made of nucleotides.

2. **Statement 2**: "DNA is an acidic substance found in the nucleus and first identified by F. Meischer in 1869."
- **Analysis**: This statement is correct. Friedrich Miescher discovered DNA in the nucleus and noted its acidic properties, naming it "nuclein." Although he did not know the structure, his identification is historically significant.

3. **Statement 3**: "Phosphate group is linked from 5-end with glycosidic linkage."
- **Analysis**: This statement is incorrect. The phosphate group is linked to the 5' end of the sugar via a phosphoester bond, not a glycosidic linkage. Glycosidic bonds connect sugars to nitrogenous bases in nucleotides.

4. **Statement 4**: "All four nucleotides are present in equal amounts in the strands."
- **Analysis**: This statement is incorrect. According to Chargaff's rules, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). Therefore, A and T are equal in quantity, and G and C are equal in quantity, but not all four nucleotides are present in equal amounts.

### Conclusion:
The only correct statement regarding DNA is **Statement 2**: "DNA is an acidic substance found in the nucleus and first identified by F. Meischer in 1869."