High abundant expression signals of detected miRNAs in two independent replicates show similar frequency distributions. Distributions of the expression signal count (y-axis: representing the proportion of total transcript counted and the x-axis: representing the count of signals; data in a log scale) derived from biological replicates of intracellular samples show a high degree of similarity. The empirical distributions can be interpreted as a mixture of two essentially distinct distributions. The low-abundant count (presented on the left part of the distribution) provides noise-rich data. This data shows an exponential decline of the frequency distribution suggesting that a large portion of signal have low counts. This is followed by a fairly even distribution across the log scale of counts and ended with sporadic signal that have high counts at the far end of the log scale. The high-abundant count (presented on the right part of the distribution) has a long tail and shows log-normal-like frequency distribution. The last part of the distribution shows high level of similarity in the right-size trends, which is is exploited in statistical tests for determining significances/reliable signals from mostly noise signals.
Koh et al. BMC Genomics 2010 11(Suppl 1):S6 doi:10.1186/1471-2164-11-S1-S6