**1.4 Application of BACs: Genomic sequencing, genomic imprinting, transgenic mice, vaccine development, and gene therapy**

There is increasing interest in the application of BAC technology in genomic research. High throughput determination of gains and losses of genetic material using high resolution BAC arrays and comparative genomic hybridization (CGH) have been developed into the new tools for translational research in solid tumors and neurodegenerative disorders (Cowell and Nowak 2003; Cowell 2004; Costa, Meijer et al. 2008; Lu 2009). Among a large number of approaches for sequencing, BAC technology is becoming the most robust method for genome sequencing. The BAC-by-BAC technique uses an overlapping tilling path of large genomic fragments (150-200 kb) maintained within BACs. Every individual BAC is shotgun sequenced. Many short reads are assembled to produce the sequence of the BACs, where these large overlapping sequences of the BACs are assembled to produce the who genome sequence (Imelfort, Batley et al. 2009). BACs have also been used in mammalian genome mapping (Schalkwyk, Francis et al. 1995), genomic imprinting (Tunster, Van De Pette et al. 2011), vaccine development and gene therapy (Magin-Lachmann, Kotzamanis et al. 2004; Warden, Tang et al. 2011). Studies of the evolutionary history and functional dynamics of sex chromosomes have recently been possible using BAC libraries (Janes, Valenzuela et al. 2011). In this chapter we will review some applications of BACs in viral and non-viral gene functional studies.
