My professor was talking about double mutant analysis with null mutants, and how double mutant analysis won't work with hypomorphs. I really don't understand the concept of double mutant analysis.
He was talking about pathways - if A and B are in the same pathway, then you would mutate A and he said something about the phenotype being identical. If A and B are in different pathways, you could mutate both of them and there would be a "stronger" phenotype.
He also said it would only work with null mutants, not with hypomorphs, because with hypomorphs some of the pathway would still be active, not completely shut off.
I really don't understand any of this - what a double mutant is, the whole pathway thing, why the phenotype is "identical" or "stronger", or why you use hypomorphs. I would really appreciate a rundown on the idea of double mutant analysis because my professor's explanation was so unclear. Thanks in advance.