Genetic Distance and Markers Used in Linkage Mapping

In this chapter, we focus on maps and markers used for a linkage analysis. More detail regarding the actual linkage analysis methodology follows in Chapter 11. There are two major types of maps: genetic maps and physical maps. Genetic maps indicate the expected number of meiotic crossover events between two loci on a chromosome and are measured in centiMorgans (cM). Physical maps use molecular techniques, such as DNA sequencing, to determine the location of markers on a chromosome and are measured in base pairs (bp). Linkage analysis relies on genetic maps, and hence they are discussed in this chapter. In addition to a discussion of genetic maps and various map functions, we also discuss the selection of markers for a linkage analysis, including the more traditional microsatellite markers and the newer single nucleotide polymorphism (SNP) markers.