Microsatellites are tandem repeats of simple sequence, 2–6 bp, that occur abundantly and at random throughout most eukaryotic genomes. They are typically short, often <100 bp long, and are embedded within a unique sequence. Thus, they are ideal for in vitro amplification by the polymerase chain reaction (PCR). The high degree of polymorphism, owing to variation in the number of repeat units, and the stability displayed by micros atellites make them perfect markers for use in constructing high-resolution genetic maps to identify susceptibility loci involved in common genetic diseases (1 ). In addition to their applications in genome mapping and positional cloning, these markers have been applied in fields as diverse as tumor biology, forensic identification, population genetic analysis, and the construction of human evolutionary trees. This chapter is confined to the analysis of chromosomal deletions.
