This is a YEtype(episomal) yeast shuttle vector. It encodes the beta galactosidase alpha peptide for bluewhite color detection of inserts and also has the T7 and T3 promoters for in vitro RNA synthesis and priming sites for sequencing. It also contains the REP3 and FRT sequences necessary for high copy propagation in yeast. In S. cerevisiae, the copy number is about 20 per haploid cell. In nonselective growth, plasmids are lost through mitotic segregation at rates in the range of 4.6 +/ 0.6% of progeny per doubling. The order of the major features in this plasmid is: ori(f1) lacZ T7 promoter MCS (KpnISacI) T3 promoter lacI ori(pMB1) ampR ori(2 micron) LEU2