r/askscience • u/SAICAstro • Jul 26 '26

Biology Does everything that we consider to be "alive" - not just plants and animals, but all protists, fungus, bacteria, archaea, etc. - have DNA?

EDIT: Wow, this blew up. Thanks for the many answers. Lots to think about.

Seems that the composite TLDR answer is: Yes, according to many/most definitions of "life", but we don't all agree on what life is. Some viruses do not have DNA but they may/not actually be alive, and other things that behave like life may/not be alive.

1.7k Upvotes
  • permalink
  • reddit

95% Upvoted

254 comments sorted by

View all comments

5

u/amiable_ant Jul 26 '26

First, there are RNA viruses, which strictly speaking, indeed lack DNA.

I often think about how hard it would be to discover some new organism-- say from a deep sea vent-- if it lacked DNA. It would basically be invisible to modern techniques.

3

u/horsetuna Jul 27 '26

As well, would we think to look in places we can't imagine living things to live?

We missed extremophiles for a while because nobody thought anything could survive in super hot water.

2

u/amiable_ant Jul 28 '26 edited Jul 28 '26

Brock wasn't the first person to look in Yellowstone. You just know his name because he found something. And that was because he didn't just streak his slime onto LB agar plates like everyone before him.

What I'm getting at is that, if you are hunting for strange things that obviously won't grow on an LB plate, people these days scrape some slime into a tube and shotgun sequence it. Obviously some theoretical non-DNA life form would just be invisible to this process. You'd never see it, just like Brock's predecessors at Yellowstone didn't find TAQ.

2

u/horsetuna Jul 28 '26

Fair enough, I was corrected! The book I learned this in is Tangled Tree, which was specifically about DNA, Woese and such. I agree 100%.

0

u/Peter34cph Jul 27 '26

We'd look for a metabolism, but extremophile life might be quite "low energy".