Recall: Mutants in the same complementation group do not complement each other (negative result)
: Mutants in different complementation groups complement each other (positive result)
To determine whether the mutations in the seven strains leading to the wingless phenotype are in the same gene, your lab sets up complementation tests. You obtain the following results ("+" indicates that complementation was observed; "-" indicates that no complementation was observed).
How many different genes are contributing to the wingless phenotypes in these mutant fly strains?