Update RNAextraction_protocol.md

assays/RNA_Extraction/protocols/RNAextraction_protocol.md

 RNA was extracted from approximately 50 mg of tissue using a Zymo DirectZol miniprep Kit.
 
 A DNase digestion was performed on the RNA extractions using Baseline-ZERO DNase (Epicenter).
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+Samples were run on a 1% agarose gel to check quality.