In 1985, David Garfinkel, Jef Bocke, and Gerald Fink showed that Ty elements do transpose but through Ribonucleic acid (RNA) intermediate.
They began altering yeast Tyl element cloned on plasmid. Near one end of the plasmid they inserted a promoter that can be activated by the addition of galactose to the medium. Then they introduced an intron from yeast into coding region of the Ty transposon. The frequency of transposition of the altered Ty element was increased greatly by the addition of galactose.
This is because the galactose stimulated the transcription of Ty Deoxyribonucleic acid (DNA) into RNA beginning at the galactose sensitive promoter. The researchers found that the intron had been removed from the transposed Ty DNA.
The introns are spliced only in the course of RNA processing. So, the transposed Ty DNA must have been copied from an RNA intermediate.