When looking at the average copy number for genes sequenced on chromosome 1p and 19q for each case, there is a distinct difference in the distribution of average copy number for cases of oligodendroglioma versus IDH-mutant and –wild type infiltrating astrocytoma that corresponds to the cut-off at a value of 1.65 (Fig. 2c, d). Here, IDH1 is linked to oligodendroglioma.