 There are some sites that have been detected to be methylated at a higher frequency in tumor tissues than normal tissues.These sites are mostly within the proximal promoter; however, some are in the 5’ UTR as well and there is a lot of interindividual variability in the cytosine methylation in these regions.A study in 1993 compared the mouse "NF1" cDNA to the human transcript and found that both the untranslated regions and coding regions were highly conserved.