Chapter 5 Genetic Dissection of Developmental Pathways

The chapter discusses the construction and interpretation of phenotypes of double mutants, screening for and analysis of extragenic suppressors, along with the issues regarding complex pathways and genetic redundancy. The chapter also explains the practical aspects of how models of developmental pathways are built in Caenorhabditis elegans. Three basic strategies for constructing double mutants are outlined in this chapter. The first method is the simplest, and involves taking animals carrying the single mutations and using them directly to make the double mutants. The second method used for construction involves using a closely linked marker in cis to each gene of interest. The construction then involves making the strain carrying both marked chromosomes. The advantage of this method is that the strain can be constructed by simply following the mutations used as markers without regard to the phenotypes of interest. The best method for determining epistatic relationships involves using linked markers in trans to the mutations of interest. This eliminates nonspecific marker effects, while ensuring that the double mutation of the two genes of interest is actually being constructed.