Update Tuesday/GREAT/GREAT_analysis_forEpigenomicData.md

Tuesday/GREAT/GREAT_analysis_forEpigenomicData.md

@@ -22,6 +22,13 @@ ChIPseq analyis done using hg19.
 </details>
 
 
+<details>
+  <summary markdown="span">Peaks have been called using the hg19 Human reference genome. Why is this information important?</summary>
+Because gene annotation, including gene location varies between assemblies.
+
+</details>
+
+
 ## Perfom analysis 
 
 * Go to http://great.stanford.edu/public/html/