RNA integrity

There are several ways to assess the quality (also called integrity) of the isolated RNA.

One quick and inexpensive method is electrophoresis, by running the RNA sample in an agarose gel and looking at the resulting ribosomal RNA (rRNA) bands. If the bands are clear and bright, and correspond to the expected size compared to the DNA ladder, the RNA is of good quality. The absence of these bands, together with the presence of a smear, indicates that the RNA sample is degraded.

Figure 1. Example of an RNA agarose gel

Another and more sophisticated way to assess the quality of RNAs is to use microfluidic analysis, where you load tinny amounts of RNA onto a chip to get a RNA Quality Index (RQI) or RNA Integrity Number (RIN), which is between 0 and 10 (0 being totally degraded and 10 being completely intact). Samples with RIN or RQI above 7 are considered good enough for further analysis.