We are keenly interested in transposable element biology, since these elements represent a major component of eukaryotic genomes, and we are also interested in removing repeats in general. The dominant view of transposon biology is that transposons are genome parasites that play no essential role in the genome. This is not in conflict with the observation that transposons have clearly been “domesticated” to play critical biological roles, such as the vertebrate adaptive immune system. When transposons are domesticated they generally lose their ability to transpose. Preliminary studies suggest yeast retrotransposons are indeed dispensable, but to our knowledge, eukaryotes that completely lack transposon sequences are exceedingly rare. Thus, we will test the hypothesis that transposon-free yeast chromosomes can be synthesized and maintained. As it is possible that during diminution of transposon copy numbers, the remaining Ty1 transposons will be activated to mobilize, the SPT3 gene, required for Ty1 transposon transcription, can be deleted. Also, we relocate the highly preferred targets of Ty1 transposition, the tRNA genes, as we go along, minimizing the probability of new insertions into the synthetic chromosome regions. Recent studies point to tRNA regions as hotspots for genomic instability.