I have a bunch of samples which are positive for a particular mutation and originating from a specific geographical location. If I go for sequencing, how much area around the mutation needs to be sequenced? I do not have parent's DNA for all the mutation positive samples. Would I still be able to carry out phasing based on the small number of trios that I have?

If I go for microsatellite screening then how do I select the candidate microsatellites around the mutation (as in what is the basis of selection?