Three parts of the gene that do not appear in the final mrna

Introns

Explanation:

In RNA processing event commonly known as RNA splicing, some non-required parts of pre-mRNA are removed. These non-required parts are Introns also known as junk sequences which are removed by spliceosome (a complex of protein-and-RNA). Later the good parts i.e exons are assembled together back to back. Thus, final mature mRNA consists of pasted exons that are later removed out of the nucleus.  

not sure if this is what you'r looking for eubacteria and archaebacteria