A gene is a sequence of DNA or RNA that codes for a molecule that has a unique function. During gene expression, the DNA is copied into RNA. The transmission of genes to the next generation is the basis of inheritance of phenotypic traits. The study of the structure and function of genes at the molecular level is approached from the discipline of molecular genetics, which is a branch of molecular biology. It explores the aspects of heredity, variation and mutation by studying chromosomes and gene expression. The understanding of gene amplification techniques, particularly polymerase chain reaction and molecular cloning, separation and detection of DNA and mRNA, etc. are vital to the understanding of the molecular biology of genes. This book aims to shed light on some of the unexplored aspects of this area of study. Some of the diverse topics covered herein address the significant aspects of molecular biology of the gene. In this book, constant effort has been made to make the understanding of the difficult concepts, as easy and informative as possible for the readers.