JavaScript must be enabled in order to use this site.Please enable JavaScript in your browser and refresh the page. Three positions with ambiguity codes Three positions on chromosome 3 are masked with 'N' in the UCSC version of the hg19/GRCh37 reference genome. These positions have IUPAC ambiguity codes in our hg19 version: M—IUPAC code for A or C nucleotides P—IUPAC code for A or G nucleotides Position IUPAC ambiguity code in hg19 reference Hard masked character in UCSC hg19 60830534 M N 60830763 R N 60830764 R N Related Topics Parent topic: hg19 reference ×