SUMMARY (To be printed on this form) Phosphoramidite derivatives of a nucleoside analogue bearing photoswitchable ortho, meta and para-azobenzene moieties were synthesized and used to incorporate the photoswitchable azobenzene group proximal to the 5' and 3' ends of deoxyoligonucIeotide primers (12mers) of the glyceraldehydes-3-phosphate dehydrogenase (GAPDH) gene. The photochemical E~Z isomerisation of azobenzene appended primers was investigated by UV/vis spectroscopy and RP-HPLC. Melting studies were also performed to determine the Tm of the primers. Isothermal primer extension reactions were performed with Klenow fragment at the dark- adapted and irradiated photo stationary states. This revealed that only the para-azobenzene perturbed the extension by the enzyme. Further investigation with time course experiments to determine a yield using fluorescent fluorescein label and explore the possibility of photoswitchable DNA amplification using the para-azobenzene primers. OligonucIeotides bearing a novel photoswitchable moiety, phenylazopyridine, have been prepared. Directed Michaelis-Arbuzov reactions of support-bound internucleotide phosphite triesters with alkane-diamines were effected in the presence of iodine. The primary amine functionalised oligonucleotides were subsequently purified trityl on. This enabled resolution offast- and slow-isomers of oligomers.