Organic chemistry for medicine and biology students Chem 2311 Chapter 18 Nucleotides and Nucleic acids By Prof. Dr. Adel M. Awadallah Islamic University of Gaza

Nucleic acids (DNA & RNA) are linear, chain macromolecules that were first isolated from cell nuclei. They have a backbone of sugar molecules, each with a base attached, connected by phosphate links.

Nucleosides N-Glycosides

A nucleoside is an N-Glycoside. The pyrimidine or purine base is connected to the anomeric carbon of the sugar. The pyrimidines are connected at N-1 and the purines are connected at N-9.

Nucleosides are water soluble. They can be hydrolyzed by aqueous acid or enzymes to the sugar and heterocyclic base

The primary structure of DNA

Sequencing Nucleic Acids The smallest DNA molecules contains at least 5000 nucleotide units Some contains 1 million or more nucleotide units The strategy relies on breaking the DNA into small identifiable fragments using a combination of enzymatic (restriction endonucleases) and chemical reactions Sangar (born 1918) sequenced a virus Chromosome with 5375 nucleotide units 1958 he was awarded a Nobel prize in chemistry “ for his work on the structure of proteins, especially that of insulin" In 1980, Walter Gilbert and Sanger shared half of the chemistry prize "for their contributions concerning the determination of base sequences in nucleic acids".Walter Gilbert 1985 sequence 170,000 nucleotide unit

Secondery Structure of Nucleic Acids * Two right handed helices 10 base pairs for every turn A = T and G = C Human DNA A = B = 30 % each G = C = 20 % each

A = T and G = C

DNA Replication

The Polymerase chain reaction PCR PCR is a technique for making many copies of a specific DNA sequence (amplification)