Abstract: Methods are described for construction of long synthetic arrays of DNA repeats, such as alphoid repeats or other repeat sequences. The methods include concatamerization of DNA into short repeats (for instance using rolling circle amplification or directional in vitro ligation), followed by assembling the short repeats into long arrays by homologous recombination during transformation into microbe cells. These methods can be described generally as Recombinational Amplification of Repeats (RAR). The long arrays are engineered centromere-like regions that allow one to construct mammalian artificial chromosomes with a predefined centromeric region structure. Artificial chromosomes, including human artificial chromosomes with a regulated centromere, and methods of their use are also provided.