Fig. 1. Extrachromosomal arrays for mosaic analysis in C. elegans. (A) Mini-chromosomes, called extrachromosomal arrays, form in vivo from DNA that has been injected into the syncytial part of the gonad of hermaphrodites. Green circles represent plasmids that contain a marker gene that cell-autonomously expresses green fluorescent protein (GFP) in nuclei of transgenic worms; blue circles represent plasmids that contain a wild-type copy of a gene under study. (B) An array can contain multiple copies of each type of injected DNA. Shown in green is the marker gene that expresses GFP in nuclei. In blue are wild-type copies of the gene under study. Endogenous copies of the blue gene have a loss-of-function mutation, as indicated by a red line. The wild-type copies on the array fully complement the mutant copies on the homologous chromosomes.