Recombinant DNA technology, gene library, probes, amplification techniques, hybridization and blot techniques, cytogenetic techniques, mutation detection techniques, DNA sequencing techniques, next generation sequencing, transgenic animals, hybridoma technique, RFLP, stem cell biology, gene therapy, human genome project, omics of molecular biology, bioinformatic and genomic sources, techniques to study proteomics and linkage, and association studies are covered throughout this chapter. Gene library is a collection of recombinant DNA clones generated from a specific source. Two types of gene library are genomic DNA library and cDNA library. DNA sequencing techniques are Sanger’s technique (controlled chain termination method), maxam and gilbert chemical cleavage method, and next generation sequencing (NGS) which are explained briefly in this chapter. Foreign genes can be introduced into fertilized egg. Animal that develop from such fertilized egg is called a transgenic animal. At the end of the chapter, there are 59 multiple choice questions are also given along with their explanatory answers.