63] Identification of genomic sequences corresponding to cDNA clones

Abstract

The general methods applicable to the isolation of genomic sequences from phage lambda or cosmid libraries have been described. This chapter presents strategies for the investigation of genes that occur in several identical or nonidentical copies per genome, or that share a common conserved domain with other genes. The methods discussed are applicable both to the identification of the genes in Southern blots and to their isolation from libraries. Furthermore, the methods are well suited for the analysis of homologous genes in different species. A high proportion of genes in eukaryotes are known to be members of multigene families. Carefully controlled hybridization conditions and well-tailored probes are powerful tools in the isolation and analysis of genes which share a common domain or are members of multigene families. This chapter consists of a short review of recommended strategies and relevant parameters, which have been discussed in more detail earlier. Using three examples from the authors' analysis of the silk moth choriun locus, they demonstrate how powerful carefully tailored short single-stranded probes can be in the analysis of closely related gene copies.