Organic chemistry for medicine and biology students

Chem 2311

Chapter 18Nucleotides 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.

NucleosidesN-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".

• 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)