The book Molecular Biology has been kept simple as far as possible, so that the students may learn without having to first assimilate complex terminology. The book contains essential facts and overloading it with estoric details, only of interest to a minute proportion of the scientific community, has been avoided. The book contains more than 125 line diagrams, which are easy to understand, memorize and reproduce at a later date. This is invariably useful while explaining a difficult concept to others as well as during examinations. Complex three-dimensional colour figures have been avoided. Although the book was originally conceived for students of B.Sc. and M.Sc., yet the individual with a background in the sciences as well as students at other levels may benefit from its simplistic approach. Those who wish to go deeper into the subject, a few articles or books are listed at the end of each chapter as further reading . Some experiments marked with an asterisk(* ) in the book are quite suitable for doing in a laboratory, under the guidance of a teacher. This book is intended to give the reader a sound foundation of molecular biology and a flavour of the subject as it stands today.