Environmental pollution due to heavy metals is of prime importance. The unrestrained release of heavy metals into the water resources produced serious threat to the aquatic fauna including fishes. The exposure, results in pathological changes at the level of macromolecule and cell organelles. Hence, it is necessary to study molecular mechanisms of protection against deleterious factors that operate at different organismal levels and to establish toxicant specific biomarkers. Written in a simple and lucid manner, the book embodies various aspects of metallothionein gene expression in freshwater murrel, Channa punctatus due to heavy metal, cadmium exposure. It includes investigation of acute toxicity (median lethal concentration), induction and sequencing of MT gDNA and cDNA, sequence information of beta actin in murrels along with quantitative real time tissue (liver, kidney and gills) specific expression pattern of MT mRNA in the dose and duration dependent manner under the metal influence. This book should prove an invaluable asset to students, professionals and researchers in the field of biotechnology, molecular biology, environmental toxicology, toxicogenomics and fish biology.