SESSION 14

Fundamental Units of DNA and RNA: Both DNA and RNA are polymers of nucleotides. A nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base (DNA: A, T, G, C; RNA: A, U, G, C).

Formation of a Dimer: Nucleotides link through phosphodiester bonds in a condensation reaction, joining the 3'-OH of one nucleotide to the 5'-phosphate of another, forming the sugar-phosphate backbone.

Storage and Passing of Genetic Information: DNA's double-stranded helix, stabilized by complementary base pairing (A=T, G≡C), ensures accurate replication. The primary sequence encodes genetic information.

Structure of DNA vs. RNA:

• DNA is double-stranded and stable, containing deoxyribose and thymine.

• RNA is single-stranded and less stable, containing ribose and uracil.

Primary and Secondary Structures:

• DNA: Primary structure is the nucleotide sequence; secondary is the double helix.

• Proteins: Primary structure is the amino acid sequence; secondary includes α-helices and β-sheets formed via hydrogen bonds.