Question

When two mutants having the same phenotype were crossed the progeny obtained showed?

Answer 1

If two mutants when crossed give a wildtype phenotype in the progeny, it implies that the two mutations are non allelic i.e they lie on two different genes. That is why in the progeny where one wildtype copy of the gene is given by each parent, complementation occurs and a wildtype phenotype is seen. This, however, happens only for recessive mutations.