Illustration for the process of mRNA transcript degradation during RNA two-cycle amplification. The transcript of a probe set becomes shorter 3 times from the beginning to the end of two-cycle amplification. x-axis is the distance of probe from the 3’end of transcript (bp). y-axis represents the retaining probability of each position after the ith-cycle. L represents length of a transcript. a and b are degrading limits from 3’end and 5’end.