Trimmed sequences from the previous step are aligned to the reference genome using a Burrows–Wheeler aligner (BWA) and the unmapped reads are removed. The aligned reads that have the same 24-base pair tag sequence and genomic region are detected and grouped (family αβ and βα in Figure 2). Each group represents a “tag family.” Tag families with fewer than three members are not analyzed. To remove errors that arise during PCR amplification or sequencing, mutations that are supported by less than 70% of the members (reads) are filtered out from the analysis. A consensus sequence is then generated for each family using the identical sequences in each position of the remaining reads. The consensus sequence is called the SSCS. It increases the NGS accuracy to about 20 fold higher; however, this method relies on the sequencing information from single strands of DNA and therefore is sensitive to the errors induced at the first round or before PCR amplification.