Figure 3. Multiplex ligation-dependent probe amplification (MLPA) technology for detecting copy number variations. (A) The amplified products are separated by conventional MLPA based on length differences in the "stuffer sequences." The stuffer sequence, which is required to separate multiple amplicons using length-based capillary electrophoresis analysis, has potential problems such as nonspecific hybridization and nonuniform amplification. (B) Multiple targets can be specifically amplified with equal efficiency using stuffer-free MLPA by eliminating the stuffer sequence because the ligated probes are of similar size and the amplification uses common primers. RFU, relative fluorescence unit.