1.Human DNA 2.YAC vector EcoRI A CEN ORI TELB HI TEL EcoRI Bam HI TEL ORI A sfcky ends ic内y ends Recombination CEN B TEL +DNA ligase 3.Yeast artificial chromosome with inserted human DNA TEL ORI A CEN B TEL up to 1000000 nucleoides pairs Clone Cloning into a Yeast Artificial Chromosome (YAC)27