The correct statement with regard to the secondary structure of DNA/RNA is

Core Logic

DNA (Deoxyribonucleic Acid) secondary structure is typically a double-stranded helix consisting of two antiparallel polynucleotide chains. Its four primary nitrogenous bases are Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). RNA (Ribonucleic Acid) is typically single-stranded (though it can fold into complex secondary structures). It contains Uracil (U) instead of Thymine.

Step 1: Evaluate Options

(1) Incorrect: DNA is double-stranded and lacks uracil. (2) Incorrect: RNA lacks thymine. (3) Correct: DNA is a double strand helix and contains thymine. (4) Incorrect: RNA is primarily single-stranded.

Pattern Recognition

DNA = Double stranded + Thymine. RNA = Single stranded + Uracil.

Chapter Mix

Class 12 Chemistry: Biomolecules