DNA breaks can be caused by, among other things, radiation, UV rays and chemotherapy. Dr Allers said: "All organisms can use enzymes to simply glue the broken strands of DNA back together, but this is prone to error and can give rise to mutations which cause cancer. The alternative is to perform a kind of molecular gymnastics called recombination, where healthy strands of matching DNA are used to repair the broken ends. This is a complicated and time-consuming strategy to mend DNA, but avoids mutations. When the enzymes that carry out recombination are defective, cancer can develop more easily. This is what happens in patients with mutations in the BRCA breast cancer genes."

Dr Allers's research, published in the journal PLoS Genetics, shows how, unlike other organisms, Haloferax volcanii deliberately avoids using recombination to repair DNA breaks. His results suggest that other polyploid organisms, such as cancer cells, might work in much the same way. What scientists need to know now is why.

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