Smokers experience one mutation to their DNA for every 15 cigarettes they smoke, according to a study that mapped out the genetic blueprint of a lung cancer patient.
British researchers led the massive international project, which identified 23,000 mutations that bore the expected signs of damage caused by chemicals in tobacco smoke.
All cancers are caused by mistakes in the genetic code - mutations in DNA that can be triggered by environmental agents.
The scientists hope the results will help them understand the causes of cancer and to develop new treatments.
Theyfound the genetic defects ranged from single-letter changes in theperson's code to deletions or re-arrangements of hundreds of thousandsof letters.
No single mutation stood out as being the primarycause of the disease. Instead most were 'passenger' mutations thatappeared to influence the development of cancer only in combination.
Study leader Dr Peter Campbell, from the Wellcome Trust SangerInstitute in Cambridgeshire said: 'The knowledge we extract over thenext few years will have major implications for treatment.
'By identifying all the cancer genes we will be able to develop new drugs that target the specific mutated genes and work out which patients will benefit from these novel treatments.'
Dr Andy Futreal, also from the Wellcome Trust, said: 'Cancers occur when control of cell behaviour is lost - cells grow how, when and where they shouldn't.
'Mutations in DNA caused by, for example, cigarette smoke are passed on to every subsequent generation of daughter cells, a permanent record of the damage done.
'Like an archaeologist, we can begin to reconstruct the history of the cancer clone - revealing a record of past exposure and accumulated damage in the genome.'

Read More @http://www.buzorpages.com/2016/06/smoking-just-15-cigarettes-harms-your.html