In genetic engineering experiments, the gene or any DNA segment is first inserted into a vector, but this chimeric vector with foregin gene is incapable of multiplying, so that is transferred into living cells of bacteria or eukaryotes, where it can multiply with the host cells. These host cells can be a variety of cells and the choice will usually depend upon the objective and the limitation which a vector or a host cell may impose. In this method DNA can be cut at the desired positions both in the vector and in the clone, without having staggered cuts. Restriction enzymes are used to cut a duplex DNA at the same place in both the DNA strands. The broken ends are then used for joining with the two ends of another DNA molecule .