Chapter 4 Genetic Mapping with Polymorphic Sequence-Tagged Sites

This chapter focuses on genetic mapping with polymorphic sequence-tagged sites (STSs), and its advantages. This mapping method offers a number of advantages over standard procedures. (1) It is rapid and requires only a single interstrain cross rather than a succession of crosses involving many different strains and requiring an elapsed time of several weeks. (2) STSs behave as dominant markers, permitting efficient and sensitive mapping strategies. In contrast, most conventional mapping in Caenorhabditis elegans uses recessive visible markers and less efficient strategies to detect linkage. (3) STSs can be scored in embryos. This permits efficient mapping of lethal mutations because the markers can be scored in lethal homozygotes that have arrested during embryonic development. (4) X-linked STS markers can be easily introduced into a mapping strain through males. In contrast, mapping on X with visible markers is often complicated by ineffective mating of hemizygous mutant males, and may require the construction of XX tra-l males. This mapping technique may permit new kinds of genetic analysis in C. elegans. One example is the mapping of multiple factors that contribute to quantitative traits.