Abstract: We describe a polymorphic variant of a BIM {BCL2L11) gene which comprises, in 5? to 3? order, the nucleotide sequence set out in SEQ ID NO: 5 followed immediately by the nucleotide sequence set out in SEQ ID NO: 7. The BIM polymorphic variant may be characterised by lacking the nucleotide sequence set out in SEQ ID NO: 6. It may be used to detect BCR-ABL-independent TKI-resistance (resistance to treatment with tyrosine kinase inhibitors) for chronic myelogenous leukaemia, c-KIT/PDGFR-independent TKI-resistance for gastrointestinal stromal tumours (GIST), EGFR-independent TKI-resistance for non-small cell lung cancer (NSCLC) or JAK2-independent TKI-resistance for a myeloproliferative disorder, in an individual comprising such a polymorphism.