HPRT1 and neoplasm: This is apparent considering that in the experiments presented here, a minimum of 45% of clones were found with the same wild type sequence, while a maximum of 5 clones out of 40 were found with an identical mutated position (HPRT transcripts showing (A>G) at nucleotide position 386 in tumour tissue of patient A), corresponding to 15% relative abundance (Table 1).