Genetic Interaction, Epistasis, Modifiers

Biological processes in an organism are interconnected and regulated by a network of genes. Therefore, the genetic dissection of their functional relationships is crucial for understanding the mechanism of biological processes. In this chapter, we will study genetic interactions between mutations. The function of a gene is reflected in the phenotype caused by the loss of a gene function. Phenotypes can be modified by an interaction between mutations in two genes. Genetic interaction analysis is essential in studying the relationship between genes by providing clues as to whether two genes act in the same or related processes. EpistasisEpistasis is the relationship between the phenotypes of mutated genes. Epistasis analysis of genetic components has been pivotal for dissecting diverse intercellular signaling pathways. Examples of epistasis tests are discussed using genetic analysis of developmental pathways in C. elegans. Mutations in interacting genes can easily modify a sensitized mutant phenotype or genetic background. Thus, genetic modification can be an efficient tool for identifying interacting genes in genetic pathways. Strategies of genetic screens for such modifiersmodifier in Drosophila and mice will also be introduced.