Strategizing a Mutant Screen
When organizing a mutant screen, one must consider several key questions that will direct the success of such a screen. What is the ultimate goal? Are the mutations going to be mapped? How does one know that the observed phenotypes are a result of heritable mutations? This section offers insight into potential pitfalls that one might consider before embarking upon a large-scale mutant screen.
The first question is to ask yourself what you would like to gain from the screen. Are you trying to find a specific group of mutants? Are you trying to determine what background mutations are present? Are you looking for random mutations? By answering the first question, the researcher can surmise a better idea of what type of population to use for screening.
If the mutations are going to be mapped, it is of the utmost importance that you choose your parents wisely and keep track of lineage thoroughly. How the mapping will be carried out will dictate which crosses are the most important. In general for positional mapping, it's best that the maternal side and paternal side be polymorphic between the two strains.
To determine whether an observed phenotype is the result of a heritable mutation requires testing the progeny of the original founder using a wild type outcross of the female. This may be accomplished with brother-sister matings or son-mother backcrosses, but it may be somewhat easier to gynogenetically test all the female offspring to isolate the carriers first. Once there is an established group of carrier females, males can be mated to the known carriers to establish whether they are carriers themselves.