In studies of myogenesis and muscle contraction in Caenorhabditis elegans, more than 20 genes have been found that affect muscle structure. Of these, one gene,
unc-54 I, has proved to be especially well suited for a detailed molecular genetic analysis. The
unc-54 gene codes for the major myosin heavy chain of the body-wall musculature, with one or more unidentified genes coding for a minor body-wall myosin as well as pharyngeal and other myosins. More than 100 independently isolated mutations have been found for the
unc-54 gene, and these have served as the basis for an increasingly sophisticated analysis of the gene and its products. Whereas others have focused on the cloning and sequencing of the gene or the effects of mutants on thick filament formation, our efforts have concentrated on a thorough genetic analysis of the gene. These studies include the isolation of new alleles of
unc-54, the construction of a fine-structure map of the gene, and the interpretation of this genetic map in physical terms.