In sequence window, there is one option called "Fix residue block". What exactly is the functionality of this option is multiple sequence alignment? Does it work in making particular residue blocks fixed or particular sequences in the multiple sequence alignment? I want to know how we can keep a set of sequences (2 or more) in the multiple sequence alignment fixed so that the remaining sequences will not affect those sequences when we run next round of alignment. This will be helpful in correcting the sequence alignment which have very low sequence identity and when we have more than 100 sequences in the alignment. Could anyone suggest if I can do it in Discovery studio? If not, recommendation of the suitable program for this operation would be appreciated.