ABSTRACT
An organism contains large numbers of cells that consists of the same set of genes but only a small number of genes express inside a particular cell at a particular period of time. Among individuals of the same species also, the genes may present in different allelic forms and thus show varied expression. This phenomenon is known as differential gene expression. Genetic makeup controls diverse events ranging from evolution to the physiology of an organism, and in order to survive the regularly changing environment, regulation of gene expression is important. Advancement in the technology for analysis of gene expression has led to deep understanding of not only patterns of gene expression but also of genome as a whole. Many methods are used to study gene expression. Some of them are restricted to analyze only one gene or small set of genes. In recent times, new advancements in techniques to study gene expression have made it possible to study large numbers of genes at a same time. Techniques for analysis of gene expression have come a long way from northern blotting, In Situ Hybridization (ISH), polymerase chain reaction (PCR), quantitative real-time PCR (qRT-PCR) to microarrays. This chapter provides information on basic principles, applications, advantages and disadvantages of these techniques.
