Tracking DNA helps scientists trace origins of genetic errors

Scientists have shed light on how naturally occurring mutations can be introduced into our DNA.

The study, which focuses on how DNA replicates every time a cell divides, helps to make clear previously unexplained patterns in how our DNA changes over time. It also provides new insight into how the human genome has been shaped throughout evolution.

Researchers have devised a technique that helps them better understand the DNA replication process and to track where mistakes are likely to happen.

The study has revealed that some of the genetic switches that control when genes are activated are likely to be hotspots for DNA flaws, or mutations, to develop.

University of Edinburgh researchers developed a method to label - and track - pieces of new DNA as they are made and to identify which copying enzyme is responsible.

Several copying enzymes - called polymerases - are involved. One polymerase first makes short stretches of DNA that act as a scaffold so that the other copying enzymes can then replicate the remaining DNA.

As this scaffold DNA contains errors, the standard model assumed all of it was removed during the process. However, the researchers found that a small but significant fraction - up to 1.5 per cent - of the finished DNA is left-over scaffold.

These scaffold sections, and the mistakes they contain, become trapped in the DNA.

This tends to occur at points in the important regulatory switches that often control when genes are switched on and off. These sites are therefore more likely than other regions to have trapped scaffold DNA and its associated errors.

Mistakes in these crucial genetic sequences can change or destroy the regulatory switch, which can lead to genetic disease, alter susceptibility to common diseases or contribute to the development of cancer.

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Tracking DNA helps scientists trace origins of genetic errors