But resistance eventually builds in many cases, and doctors have been struggling to explain why. The explanation lies with newly uncovered mutations in BRCA2, according to two studies, published online by the British journal Nature. In its healthy form, BRCA2 has the job of repairing damaged DNA. But a flawed version of BRCA2 disrupts that ability, which increases the risk that mutant cells survive and develop into tumours. At the same time, though, BRCA2-type cancers are -- initially -- very responsive to chemotherapy. Read more at: http://news.yahoo.com/s/afp/20080211/ts_afp/healthdiseasewomencancer_080210213157