You have isolated five mutations (1 to 5) in the yeast Saccharomyces cerevisiae that make the haploid cells unable to grow in the absence of histidine. Each haploid mutant can be mated with any of the other ones, forming diploid cells that either can (+) or cannot (-) grow in the absence of histidine, as indicated in the following complementation table. How many complementation groups do these mutations represent? Each complementation group typically corresponds to a separate gene.