Select the statement that is correctly relatable with DNA.

Options

A. Double helical structure in which two strands of polynucleotide runs parallel to each other.
B. The chief bond to hold the monomeric units together is the H- bonds.
C. N- bases projected more or less perpendicular to back bone and faces inside.
D. DNA is a homopolymer of nucleosides.

Answer

To solve the question regarding which statement correctly relates to DNA, we will analyze each statement provided:

1. **Statement 1:** "DNA has a double helical structure in which two strands of polynucleotide run parallel to each other."
- **Analysis:** This statement is incorrect. DNA consists of two strands that are anti-parallel, meaning one strand runs in the 5' to 3' direction while the other runs in the 3' to 5' direction. Therefore, this statement does not accurately describe DNA.

2. **Statement 2:** "The chief bond to hold the monomeric units together is that hydrogen bond."
- **Analysis:** This statement is also incorrect. While hydrogen bonds do play a role in stabilizing the base pairs between the two strands of DNA, the primary bond that holds the nucleotides (the monomeric units) together within a single strand of DNA is the phosphodiester bond. Thus, this statement is misleading.

3. **Statement 3:** "N bases projected more or less perpendicular to the backbone and faces inside."
- **Analysis:** This statement is correct. In the structure of DNA, the nitrogenous bases (adenine, guanine, cytosine, and thymine) are indeed oriented perpendicular to the sugar-phosphate backbone and face inward, forming the rungs of the helical ladder. This accurately describes the structure of DNA.

4. **Statement 4:** "DNA is a homopolymer of nucleosides."
- **Analysis:** This statement is incorrect. DNA is not a homopolymer of nucleosides; rather, it is a polymer of nucleotides. Nucleotides consist of a phosphate group, a sugar (deoxyribose in the case of DNA), and a nitrogenous base. Therefore, this statement is also false.

**Conclusion:** The correct statement that relates to DNA is **Statement 3**.