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.