Question

which element is found in both dna and protein?
○ sulfur
○ sodium
○ nitrogen
○ chlorine

Explanation:

1. Analyze the composition of DNA: DNA is made up of nucleotides, and each nucleotide contains a nitrogen - containing base (adenine, thymine, guanine, cytosine), along with sugar and phosphate. So, nitrogen is a component of DNA.
2. Analyze the composition of proteins: Proteins are made up of amino acids. Amino acids contain an amino group ($-NH_2$) which has nitrogen. Some amino acids (like cysteine and methionine) contain sulfur, but not all proteins have sulfur. Sodium and chlorine are not typical components of either DNA or proteins in their basic structural makeup.
3. Evaluate the options:

• Sulfur: Not all proteins have sulfur, and DNA does not contain sulfur.
• Sodium: Not a component of DNA or proteins in their fundamental structure.
• Nitrogen: Present in the nitrogen - containing bases of DNA and in the amino groups of amino acids (which make up proteins).
• Chlorine: Not a component of DNA or proteins.

Answer:

C. nitrogen