Overview of the seamless cloning of repetitive sequences for the production of Poly-Q proteins. (A) Genealogy of the pMK1-vectors. A pool of different pMK1 vectors was generated by elongation cycles using double-stranded oligonucleotides or Poly-Q encoding DNA fragments derived from pre-existing pMK1-Qn vectors. (B) Repetitive sequences of different lengths cloned by the described strategy in (A). pMK1-Qn plasmids encoding indicated Poly-Q stretches were digested with EcoRI (cuts 77 bp upstream of BsaI) and SacI. The inserts were separated on a 2% agarose gel and visualized by ethidium bromide (EtBr) staining.