Practice question

Standard complementation tables score growth or phenotype of trans heterozygote using plus symbol to indicate appearance of wild-type trait meaning successful complementation and functional restoration. Plus signifies both parental genomes together provide functional products compensating recessive defects restoring enzymatic flux or structural function. Mutations producing plus when paired belong to different complementation groups and different genes. Convention originates from microbial auxotroph studies where plus denotes growth on minimal medium and minus denotes failure now extended to Drosophila cis-trans tests and somatic hybrids.