Thanks for the help! Yes, what I'm thinking about is when an event of alternative splicing happens but then it generates some kind of mutation. So what you are saying is that I should search for differential splicing, is that it? Can you explain me or give me some links of what it consists on?
About the second question, in first place I must say that it was some biology experts that asked me about this, so I'm also trying to, somehow, get their point of view. Given this, is there way for, given a tophat output I can determine, for example the sequences that will have a place in mitochondrial genes?
Ps: I'm student in informatics engineer and there are some concepts of biology that often are hard for me understand at first.