B. List three post-transcriptional modification of mRNA:__4__；__5__;__6__.

3. Consider two theoretical eukaryotic transposons, A and B.Each contains an intron. Each transposes to a new location in the yeast genome and then is examined for the presence of the intron. In the new locations, you find that A has no intron, but B does. What can you conclude about the mechanisms of transposition movement for A and B from these facts? (3 points)