ATM and breast carcinoma: The estimate for ATM c.7271T>G (p.Val2424Gly) was also consistent with that found by segregation analysis.7, 13 The substantial increased risk of breast cancer associated with ATM c.7271T>G (p.Val2424Gly) could be due to the reduction in kinase activity (with near-normal protein levels) observed for ATM p.Val2424Gly,31 thus this variant is likely to be acting as a dominant negative mutation.32