I just got back from lunch and I was listening to “Science Friday” on public radio.
For the first time that I am aware of a reputable viral scientist announced that RNA has been found in the genome of some plants and animals.
A couple of items that come to mind:
RNA has different pairs of molecules in their sequences than DNA. I think one of them is Uracil (I may have that wrong). But I don’t know how RNA can be inserted into a DNA sequence.
The other thing is that some of the insertions are very toxic including Ebola, which somewhat ironically may help protect against some viral infections.
Anyway I think this is very exciting stuff as it further defines how we came to be.
You’re right about uracil - it replaces thymine in DNA. (GCTA - GCUA) pairing with adenine. Dunno why though. Uracil seems to be less stable than thymine, perhaps this ensures RNA is shorter lived in the cell - ie you don’t want RNA to stick around too long when it’s not needed - or is it destroyed in the process of transcribing proteins/whatever…?
I know that some plants - gooseberries spring to mind, and some animals - cows I think, when stressed do weird things - like express toxins in the GB case and cows I seem to remember poison their own stomach contents…? Giving the predator eating them a nasty case of the runs.
Maybe the RNA is something to do with these defense mechanisms…?
Without any understanding of the specifics, could I be permitted a dumb question? Could the RNA be vestigial defense mechanisms left over from proto cell development? The defense mechanisms of making a cell unpalatable to predators had to start somewhere. Why not at the beginning?
I’m a little surprised that Uracil isn’t replaced by Thymine during replication.
It’s just speculation, but I think that at least in part you are correct about RNA as a defense mechanism. More specifically, I think that portions of the inserted RNA sequence that encode proteins, likely work as obstacles to other viral infections during replication.
But, IIRC, in general RNA serves at least a couple of purposes in cell reproduction, and there is a lot of chemistry going on.
I think we (or at least I) need to be careful about the role of small viral insertions into the genome and the different types of RNA in a cell.
Thanks for your response.
Ed
Hi Tentative,
I don’t know as much as I would like in this area, and I have forgotten some interesting information but I will try to reconstruct something from memory.
There was an article in Scientific American a number of years ago (maybe 8 to10 years - but I’m bad at this kind of thing) called “It’s an RNA World”. The author was very famous - maybe won a Noble prize - and in any case became the head of a large bioengineering firm.
Anyway, the article claims the “Proto Soup” had become rich with RNA sequences. These sequences had many constructive properties and some of them had to do with defense mechanisms. I wish I could remember more, but I think that in some manner it is likely that there are “vestigial defense mechanisms”.