( s obtained using a one-step method and ...)Determinants of RNA Integrity and Purity

Figure 1. A Combination of Single Step Organic Extraction and Solid Phase RNA Extraction Improves RNA Quality. RNA was extracted either using single phase organic extraction (A, B) or single phase organic extraction followed by purification with Ambion's MEGAclear Kit (C, D). The RNA was stored overnight at either 20C (A, C) or 37C (B, D).

Removing Genomic DNA and Small RNAs
Other contaminants that can affect total RNA performance in downstream applications are residual DNA contamination and small RNAs such as 5S and tRNAs. Residual genomic DNA contamination is most problematic in tissues with high cell densities, such as spleen or tissue culture cells. Figure 2 shows examples of gross contamination with genomic DNA. High molecular weight genomic DNA typically migrates as a broad, larger molecular weight peak that is well separated from rRNA peaks (Panel A). Note, also, that the base-line is high in this electropherogram: this is generally a signature of underlying genomic DNA contamination. Genomic DNA that has been partially sheared can sometimes migrate between the 18S and 28S rRNA ribosomal bands (Panel B), making it difficult to accurately determine the rRNA ratio. Incomplete DNase I digestion can generate small molecular weight DNA fragments between 50200 bases in size (Panel C). The most common causes of incomplete DNA digestion are residual contaminants (high salt, residual organics, etc) that inhibit enzyme activity, or the use o
'"/>

Source: