Would aliens have DNA?

Now we're moving on to the main part of the show and this week is all about life's favourite molecule DNA,  the spiral at the heart of the cells in every living creature. So is DNA the holy grail of evolution across the Universe? Before we turn to science, let's turn to science fiction, in this story written by MIT student Alexandra Sourakov, based on an idea by Linus Pauling. Imagine a groups of aliens with similar DNA to our own, only theirs twists the other way, so there are two groups: L and D, read here by Rox Middleton.

Rox - Earth's inhabitants were famous across the galaxy for their propensity for taking in the less fortunate. So when it became apparent that the D-humans could no longer remain in their home planet, the L-humans of Earth welcomed these refugees with open arms.

How could we not. By all appearance they were our doppelgangers. Their planet's primordial slime had also spat out the secret of life, the same double helix we're all so familiar with. The difference between us was literally miniscule, almost inconsequential, they were our mirror images. Because everything was flipped in their body, they functioned perfectly fine. We didn't even have to sorry about the spread of extraterrestrial diseases because theirs did not affect us, and ours didn't leave a scratch on them. Alice's journey through the looking glass should have served as a cautionary tale...

After leading a long and extensive campaign to convince the people of planet Earth to  help our chiral brethren, the scientists finally won the polarising debate. However, since the formulation of the plan to help the D-humans there had been a few hiccups. The scientists had somehow overlooked the crucial fact that D-humans could not actually derive nutrition from L-food and so sprung up the Institute of D-Nutrition.

But the most heartbreaking hiccup of all - we were biologically incompatible.