This book delves deep into the fascinating world of molecular biology, a term first coined by William Astbury in 1945. This comprehensive book serves as an authoritative guide to the chemical and physical structures of biological macromolecules and the intricate world of genes. It offers a panoramic view of molecular biology, weaving together genetics, biochemistry, cell biology, physics, organic chemistry, and biophysical chemistry into a cohesive narrative. Spanning thirteen meticulously crafted chapters, this book begins with the fundamentals of genetic material, gradually advancing through the complexities of DNA and RNA chemistry, the organization of chromosomes in prokaryotes and eukaryotes, and the mechanisms of DNA synthesis and repair. Chapter 8 delves into the molecular mechanism of mutagenesis, shedding light on the nature and types of mutations. The latter chapters provide an in-depth analysis of RNA types and structures, RNA synthesis, the genetic code, protein biosynthesis, and the regulation of gene expression across prokaryotic and eukaryotic systems. The final chapter offers insights into selected analytical techniques used in DNA research. Designed to cater to students across various disciplines, this book aligns with the syllabi of undergraduate and postgraduate courses in biochemistry, biotechnology, bioinformatics, life sciences, molecular genetics, and medical genetics, predominantly in Indian educational institutions. It stands out with its unique inclusion of challenging questions and problems with solutions, review questions, and practical application boxes in each chapter, making it an invaluable resource for academic success and competitive examinations like NET. This book is more than a textbook; it is a beacon of knowledge that illuminates the molecular foundations of life, making complex concepts in molecular biology accessible and engaging for students and enthusiasts alike.