#recombination

How Quantum Physics Allows Us To See Back Through Space And Time

"If it weren’t for this rare transition, from higher energy spherical orbitals to lower energy spherical orbitals, our Universe would look incredibly different in detail. We would have different numbers and magnitudes of acoustic peaks in the cosmic microwave background, and hence a different set of seed fluctuations for our Universe to build its large-scale structure out of. The ionization history of our Universe would be different; it would take longer for the first stars to form; and the light from the leftover glow of the Big Bang would only take us back to 790,000 years after the Big Bang, rather than the 380,000 years we get today.

In a very real sense, there are a myriad of ways that our view into the distant Universe — to the farthest reaches of deep space where we detect the earliest signals arising after the Big Bang — that would be fundamentally less powerful if not for this one quantum mechanical transition. If we want to understand how the Universe came to be the way it is today, even on cosmic scales, it’s remarkable how subtly dependent the outcomes are on the subatomic rules of quantum physics. Without it, the sights we see looking back across space and time would be far less rich and spectacular."

What gives the Universe the properties we see today? Is it gravity, working on the largest of cosmic scales? It plays a role, but perhaps ironically, the subatomic physics that governs electron transitions within atoms is maybe even more important.

Clues from Koalas

Alongside protein-coding genes, the human genome contains many non-coding sequences, so-called 'junk DNA', including an estimated 8% of our DNA derived from retroviruses. These viruses replicate by inserting their DNA into their hosts’ genomes; if inserted into the DNA of germ cells, giving rise to ovules and sperm, they can be passed on to future generations, eventually losing their viral function. Retroviral insertions in our genome are very ancient, but a more recent, ongoing invasion has been discovered in koalas (pictured), allowing us to study this process in action. Research shows that shuffling genetic material during DNA replication, between koala retrovirus (KoRV) and more ancient retroviral elements in the genome, can quickly disable KoRV. Known as recombination, this mechanism is likely to be a key early step towards retroviral integration. As researchers continue to monitor koala retroviruses, these beloved Australian icons may help us piece together our own genome’s history.

Written by Emmanuelle Briolat

Image by Emmanuelle Briolat

Research from the Department of Wildlife Diseases, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany; Australian Museum Research Institute; Department of Animal Sciences, University of Illinois at Urbana–Champaign

Image copyright held by the photographer

Research published in PNAS, August 2018