9.  Boeke, Fink, and their coworkers demonstrated that transposition of the Ty element in yeast is through an RNA intermediate. They constructed a plasmid by using a Ty element into which they inserted not only a promoter that can be activated by galactose but also an intron into the Ty element’s coding region. First, the frequency of transposition was greatly increased by the addition of galactose, indicating that an increase in transcription (and production of RNA) was correlated to rates of transposition. More importantly, after transposition, they found that the newly transposed Ty DNA lacked the intron sequence. Because intron splicing takes place only during RNA processing, there must have been an RNA intermediate in the transposition event.

13.  Some transposable elements have evolved strategies to insert into safe havens, regions of the genome where they will do minimal harm. Safe havens include duplicate genes (such as tRNA or rRNA genes) and other transposable elements. Safe havens in bacterial genomes might be very specific sequences between genes or the repeated rRNA genes.

27.  The staggered cut will lead to a nine-base-pair target-site duplication that flanks the inserted transposon.

30.  It would not be surprising to find a SINE element in an intron of a gene rather than in an exon. Processing of the pre-mRNA would remove the transposable element as part of the intron and translation of the FB enzyme would not be effected.