B4 - Physical And Genetic Mapping

Abstract

This chapter provides an overview of construction of physical and genetic maps. Restriction map is the complete set of DNA restriction fragments produced by a given restriction endonuclease ordered in the same linear fashion as the fragments are aligned in the genome itself. It can be converted to a genetic map by localizing genes onto individual restriction fragments. To construct a meaningful genetic map, a restriction map with a high resolution is needed. The classical and outdated procedure to convert a physical map into a genetic map is to map the relative positions of two or more gene loci by genetic crosses. Genes are localized on a physical map by DNA— DNA or DNA–RNA hybridization experiments with specific gene probes. To construct a detailed restriction map, one should start off with establishing a map with a relatively small number of restriction sites and then increasing the resolution of the map gradually. Two different approaches are used to establish the correct order of restriction fragments: one-dimensional pulsed-field gel electrophoresis (PFGE) combined with additional methods for aligning individual restriction fragments and two-dimensional PFGE.