American scientists have just created the first living artificially constructed life forms, engineered with the purpose of passing down an expanded genetic code to future generations.

The breakthrough is being heralded as a leap towards a new host of life forms whose cells will carry synthetic DNA that is completely different to the normal genetic code of natural organisms.

DNA is the building block of life, setting out our diversity in a code of four letters: G, T, C and A. From the moment the first living organism burst into being, to the world of today billions of years later, this code has dictated the diversity of creatures roaming the planet. The latest discovery, however, has introduced two new letters into the mix: X and Y.

These letters join the others as the molecules or bases that pair up in the DNA helix, and fly in the face of the common understanding that the molecules of life that constitute DNA are sacrosanct.

The researchers responsible claim that the organisms they create that carry the brand new DNA code could be engineered to churn out new drugs that otherwise could never have been made. The synthetic coding in cells could allow scientists to manufacture proteins that don't currently exist in nature, leading to a new wave of protein based medicine.

Floyd Romesberg led the team that crated this ground-breaking organism at the Scripps Research Institute in La Jolla, California. He started by inserting a loop of genetic material that combined normal DNA with two synthetic DNA bases into the E coli bug. This synthetic DNA formed a third base pair, X-Y, which can now be used to make genes – the templates cells use for proteins.

Critically, Rosemberg's team discovered that when the E coli divided it passed on both the natural and synthetic DNA to the next generation, and the next generation of bacteria did the same.

"What we have now, for the first time, is an organism that stably harbours a third base pair, and it is utterly different to the natural ones," Romesberg told the Guardian. It's a discovery that shakes our understanding of life by the scruff of the neck, challenging the preconception that DNA is somehow inalterable.

Synthetic biology, however, is a controversial topic. You don't have to have read Brave New World to understand concerns over the moral questions surrounding the issue of meddling with life's building blocks. Plus there are not-so-palatable fears that engineering artificial life forms that could eventually launch a cataclysmic environmental disaster.

What do you think of the breakthrough? Is it a step towards utopia or dystopia? Let us know in our poll or the comment section below.