Ch.1 Fundamentals of Nucleic Acid Biochemistry: An Overview

Unit of nucleic acid compised of a phosphorylated ribose sugar and a nitrogen base

• 4 bases in DNA and RNA
• *adenine
• *cytosine
• *guanine
• *thymine
• *uracile

Four nucleotide building blocks of DNA are molecules of about 700 kilodaltons (kd; one dalton is equal to the atomic mass of 1/12 of the 12 carbon isotope).

consists of a five-carbon sugar, the first carbonof which is covalently joined to a nitrogen base and the fifth carbon to a phosphate moiety

Planar carbon-nitrogen ring structure that comprises part of a nucleoside

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• Amine and ketone substitutions as well as the single or double bonds within the rings distinguish the four bases that comprise the majority of DNA

sugar derived from ribose by replacing a hydroxyl group with hydrogen 

Covalent attachment of the hydroxyl oxygen of one phosphorylated ribose (or deoxy ribose) sugar to the phosphate phosphorous of the next.

The phosphodiester backbones of the two nucleic acid chains form the helix. Nitrogen bases are oriented toward the center where the hydrogen bonds with homologous bases to stabilize the structure.

Two hydrogen bonds form between adenine and thymine.

Three hydrogen bonds form between guanine and cytosine.

published a paperon nuclein, the viscous substance extracted from cell nuclei and isolatedwhite blood cells out of seepage collected from discarded surgical bandages.

were the first to describe double helical structure of DNA (Fig. 1-1)

unit of nucleic acid comprised of a ribose sugar and a nitrogen base

Nitrogen bases with a singlering structure (thymine, cytosine) are pyrimidines.

Bases with a double ring structure (guanine, adenine) are purines.

Numbering of the positions in the nucleotide molecule starts with the ring positions of the nitrogen base, designated C or N 1, 2, 3, etc.

The carbons of the ribose sugarare numbered 1' to 5', distinguishing the sugar ring positions from those of the nitrogen base rings