Q. Which of the following elements are present in DNA?

1. Oxygen
2. Nitrogen
3. Sulphur
4. Phosphorus
5. Carbon

Select the correct option from the codes given below:
Answer: Only 1, 2, 4 & 5
Notes: DNA contains the elements carbon, hydrogen, oxygen, nitrogen, and phosphorus. Sulphur is not a constituent of DNA, but is found in some proteins. The sugar and phosphate backbone provides carbon, oxygen, and phosphorus, while the nitrogenous bases supply nitrogen and carbon. This helps differentiate DNA composition from proteins, which may contain sulphur.