This one’s real easy, you guys--super low key, not really a big deal, it’s just this
silly question that nobody’s really interested in, it’s just like….how did life begin?
Ok, obviously I’m joking.
This is one of the biggest unanswered questions in science today, and is the backbone of our
burning questions about who we are, where we come from, and if we’re alone out here.
New research has now given us clues into how exactly the fundamental molecular building
blocks of life came together in the first place.
Because that’s the central question: in the big puddly soup of pre-biotic earth--as
in, earth before living organisms--how did the perfect ingredients for life form, much
less fuse together into something that stores information and can replicate independently.
A primer on how our living cell’s work: A cell’s most important components are DNA,
RNA and a ribosome.
DNA codes for all of the essential information about what the organism is and how it works,
but it’s kept all safe and huddled away in the nucleus.
To take that information and make it into actual stuff, like proteins, an enzyme called
RNA polymerase copies sections of the DNA and makes strands of RNA, which are a like
one-sided version of DNA.
These messenger RNA strands get sent to the cell’s ribosome, where they’re converted
into the proteins our cells need for survival.
When scientists were first discovering all this complex stuff, it became an even bigger
question of how all this could have spontaneously come together as a result of organic chemistry.
To tackle this problem, some scientists suggested that perhaps life as we know it now didn’t
all spontaneously form at once exactly as it is, it was probably a little simpler...maybe
it was only RNA-based!
This hypothetical situation is what we refer to as the RNA world.
But this track of thinking is based on the idea that the self-replicating aspect of life
is what formed first.
And not everyone agrees.
Some people think that metabolization, or the ability to extract energy from your environment,
must have come first, while a third camp thinks that compartmentalisation must have come first,
a primitive version of the different internal pieces of a cell.
These divisions in the scientific community still survive, but as we’ve come to learn
more about RNA and how it can behave, it’s become clearer that it’s an essential part
of the beginning of life, if not the first thing that formed.
This is because RNA can do a really exciting thing.
Not only can it contain information that it can then replicate...but it can also fold
itself up into shapes in which it can act as an catalyst, influencing chemical reactions!
When this was discovered, we realized it was much more likely that RNA-based life could
indeed have survived and replicated all on its own...without the all the fancy add-ons
we have today.
So then we come down to the question again--how did RNA form in the first place?
Scientists have been on a quest to demonstrate how all of RNA’s component parts could have
spontaneously assembled, and new research may just bring it all together.
RNA is made up of the nucleic acids cytosine, uracil, adenine, and guanine.
A research team had shown a few years ago that a set of five simple compounds could
have given rise to cytosine and uracil with nothing more than the addition of UV light,
which there was plenty of on a primitive earth.
A different team then showed a similarly easy and plausible process for the formation of
adenine and guanine from simple building block elements.
But no one had demonstrated that these two separate reactions, producing all four RNA
nucleic acids, could have occurred in the same place at the same time...until now.
A paper that came out in 2018 showed that a simple set of molecules--oxygen, nitrogen,
methane, ammonia, water, and hydrogen cyanide, all of which would have been present on an
early version of earth--could react to form what we recognize as the uracil, adenine,
guanine and cytosine.
This work is the first experimental evidence showing that the chemistry fits--these building
blocks could have feasibly all come together at the same time, in the same place, we saw
it happen before our very eyes.
There are still a couple of missing pieces that we haven’t been able to recreate in
the lab.
For instance, how did each of the building blocks come together to link them into the
long chains that take them from nucleic acids to actual RNA?
And, keep in mind, while the RNA world is the leading theory, there is some contention
among scientists about the first inklings of life on earth.
Hopefully work like this will add to that discussion, PLUS it does represent an unprecedented
step forward in answering the most fundamental of questions: how life began.
For more on DNA and the craziness of life, check out another video of mine here.
Don’t forget to subscribe to Seeker for all your genetic information questions, and
thanks so much for watching