I believe the RNA integrity number (RIN) is inferred based on the ratio of ribosomal RNAs (18S and 28S in human samples).
Artur is right; I apologize for misleading you. The rRNA ratio is apparently not the only input considered by the algorithms used to established RIN values. According to the wikipedia page, they additionally rely on the following parameters :
"Total RNA ratio: Calculated by taking the ratio of the area under the 18S and 28S rRNA peaks to the total area under the graph, a large number here is desired, indicating much of the rRNA is still at these sizes and thus little to no degradation has occurred. An ideal ratio can be seen in figure 1, where almost all of the RNA is in the 18S and 28S RNA peaks.
Height of 28S peak: Again, a large value is desired. 28S, the most prominent rRNA species, is used in RIN calculation as it is typically degraded more quickly than 18S rRNA, and so measuring its peak height allows for detection of the early stages of degradation. Again, this is seen in figure 1, where the 28S peak is the largest, and so this is good.
Fast area ratio: The fast region is the area between the 18S and 5S rRNA peaks on an electropherogram. Initially, as this value increases, it indicates degradation of the 18S and 28S rRNA to an intermediate size, though the ratio subsequently decreases as RNA degrades further, to even smaller sizes. Thus, a low value doesn't necessarily indicate either good or bad RNA integrity.
Marker height: A small number is desired here, indicating only small amounts of RNA have been degraded and proceeded to the smallest lengths, indicated by the short marker. If a large number is found here, that indicates that large amounts of the rRNAs have been degraded to small pieces that would be found closer to this marker. This situation can be seen in the 'poor quality' RNA electropherogram found in figure 2, where the height of the peak over the marker (far left) is very large, so the RNA has been greatly degraded."
- Badges
- Science topic
- Similar topics
- Cell Biology
- Methods