Viewing a single comment thread. View all comments

FrostReaver t1_jbnianq wrote

Reply to comment by Ragondux in I just learned that the known shortest DNA in an “organism” is about 1700 base pairs in a certain virus. Is there a minimum amount of “code” required for an organism (or virus) to function in any capacity? by mcbergstedt

The first cells could've been a couple strands of RNA in a micelle with a protein.

74

Ragondux t1_jbnieqh wrote

There's even a theory that proteins appeared later, since RNA can do a lot of stuff by itself and have enzymatic functions.

88

Beliriel t1_jbnsf2e wrote

Yeah the base pairs of RNA can spontaneously form in nature and RNA can act like an enzyme or protein itself. Last I heard, evidence strongly hints that the world was an RNA (single strand) world before double stranding and then the more stable DNA double helix developed. But it's not conclusive.

52

HermanCainsGhost t1_jbon0d6 wrote

The “RNA world hypothesis” was what I was taught in my upper level genetics class back in 2004, so unless I am out of the loop and it has been discarded in the 20 years since, it sounds accurate to me

11

UnfinishedProjects t1_jbo8q53 wrote

I've seen this before, and I understand it, and I understand life can be created spontaneously by lightning striking in the perfect place. But what does that early early, minimal life do?? Is it about to hunt for "food"? How does it survive and replicate if it's just a few proteins that got shocked?

2

Dr_Vesuvius t1_jboah5t wrote

You’re thinking of “life” as if it were a soul, some chemicals gain a “spark of life” and then they are alive.

It’s more helpful to think of life as being those things which reproduce. This isn’t a perfect definition either, of course.

You have a primordial soup full of basic organic chemicals. Some bits of RNA, some proteins, some sugars. These chemicals are already undergoing natural selection, as more stable ones survive longer, but they aren’t undergoing evolution because there is no “descent with modification”. Maybe some chemicals, through chance, form a very simple precursor to a cell which dramatically increases their survival. They can absorb small molecules while protecting themselves from the environment. Great. Does not mean they are alive. Can that structure divide into two parts which can then both grow and divide again? That’s what makes something alive.

43

UnfinishedProjects t1_jbou27j wrote

You made me understand primordial soup for the first time. I mean I understood what they meant but I never thought about it being an actual soup of all the required ingredients.

6

Shadver t1_jbog0eo wrote

To sort of echo the other response in a different way, I find it easier to think of early life in a chemistry sense rather than a biology sense. Chemical reactions can "reproduce"(autocatalysis), and they can compete with other reactions over the starting ingredients for the reaction. We can get these sort of lifelike qualities from very simple structures that could be outcompeted by more complex and better replicating structures over time. If you're interested in more about origin of life research, I found that the YouTube channel "Professor Dave Explains" does a really good job of giving easy enough to understand explanations for stuff like this.

10

UnfinishedProjects t1_jbotuuf wrote

Okay now that actually makes perfect sense. Life is just an ongoing chemical reaction after all.

3

Teslapunk1891 t1_jboeonb wrote

I find the concept of prions to be useful in understanding this. Ofc, prions are complex proteins and massively more complex and durable than any early life-precursor would have been, but they can fold other proteins into copies of themselves. Early protoliving assemblages could have been amino acid assemblages that generally tend to replicate through a few stages, and more effective/ more complicated versions of them were able to keep replicating and working together until eventually they could form something that would be considered living.

4

triklyn t1_jbop8ul wrote

what does a prion do?

makes non-prions into prions. self-replication is the most important step. from there, imperfection will enable natural selection.

2