More than two-thirds of cancer mutations are the result of random mistakes in DNA replication that occur when normal cells divide, a new study reveals.

The study renews a debate over how much people can do to prevent cancer and how much is unavoidable.

According to The Washington Post, the mathematician Cristian Tomasetti from Johns Hopkins University has set out to determine what proportion of cancer mutations are due to unpredictable DNA-copying errors. They have opposed to the two other main contributors to cancer, environmental factors, such as smoking and obesity and inherited genes.

In conducting this research, the scientists used a mathematical model that analyzed genome sequencing and epidemiological data for 32 types of cancer. Overall they found that 66 percent of mutations that contribute to cancer are due to unavoidable DNA-replication mistakes. On the other hand, 29 percent are attributable to environmental factors and five percent to heredity.

Live Science has reported that two-thirds of cancer cases are caused by random copying errors. Scientists stated that it can take three, four or more mutations to make a cell turn malignant. But the proportion of mutations due to random copying errors varies depending on cancer.

Human cells are constantly regenerating by dividing and making new cells. Each time DNA is copied, an average of three random mistakes will occur. Scientists said, while most are harmless, a small number affect the gene that will promote cancer.

However, the researchers from Hopkins University have reported their earlier work was widely misinterpreted. The scientists took pains to stress that their study was consistent with an estimate that 40 percent of cancers are prevented. They have also urged the public to pursue a healthy lifestyle.

The new analysis report was published on March 23 in the journal Science. On the report, the researchers found a strong correlation the number of stem-cell divisions and the incidence of the disease.

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