Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Reelya]

Another useful role for carrying such "junk" around, is that it reduces the likelihood that a random mutation (say, caused by a cosmic ray particle, or by UV exposure, or (insert ionization source here) happening in a vital section of DNA. If you carry around lots of non-coding junk, a mutation there wont kill you.  If your genome is "Super efficiently lean"-- a mutation is pretty much always a bad thing.

That would protect against some types of errors but not others. e.g. single base-pair copying errors which occur at a certain frequency per base-pair wouldn't benefit from junk DNA at all, since the number of errors scales linearly with the number of DNA bases.

For radiation sources it's sort of debatable too, because other non-DNA molecules also absorb UV and cosmic rays, so having a bigger DNA target wouldn't necessarily have a meaningful protective effect on other DNA. It's a bigger target now with the extra DNA. It's possible that it would protect against free radicals that actually get into the chromosome however.

So, for each mutation source, you'd have to see whether the amount of mutations scales linearly with the number of DNA bases or not. If it does scale linearly, then more junk would also mean more mutations, hence no actual protective effect.

http://jcb.rupress.org/content/157/4/579.abstract

Well, that really suggests that since chromosomes are folded up, the protein machinery can't get into some parts of the actual chromosome, so that coding genes need to be on the surface. (The obvious analogy being how brain "activity" is all on the surface but you clearly need all the other cells too). So the junk is the necessary scaffolding that keeps the genes on the outer part of the chromosome where they can be accessed. But this idea definitely contradicts the "protection from mutation" idea above, since if the outer parts are the important parts, how can the inner parts protect them in any meaningful way?

[wierd]

The leading source of mutation is transcription error. Deletions or multi-sequence repeat caused by DNA polymerase getting stuck at part of the strand, and puking out incorrectly copied DNA during replication.  This happens when the DNA is outside of the nucleus during cell division.

If you have some %FOO chance that this will happen, regardless of what DNA is being transcribed, having a certain amount of noncoding DNA provides some tolerance from this source contributing to catastrophic mutations.

[GiglameshDespair]

I'm not really sure this is connected to space anymore.

[TheBiggerFish]

I'm not really sure this is connected to space anymore.

Radiation damage.

[Starver]

For radiation sources it's sort of debatable too, because other non-DNA molecules also absorb UV and cosmic rays, so having a bigger DNA target wouldn't necessarily have a meaningful protective effect on other DNA. It's a bigger target now with the extra DNA. It's possible that it would protect against free radicals that actually get into the chromosome however.

That is indeed something that I intended to mention, if I didn't.  Some repeating 'junk' base-pair sequences (e.g., for the sake of illustration, ATATATATATAT..., but it's probably not that, I'd have to go a-Googling to get the exact details) act as 'lightning rods', actually being more attractive to radical ions and taking damage (with or without a handy molecular tool, nearby that spots damaged ATATATATATs and repairs/neutralises it).

Given the likelihood of ATATATATAT coding for anything otherwise useful, and their tendency to be so 'attacked', that we have such strings in there (and repair functions to maintain/reinstate them) indicates that there is a 'use' which is beneficial to pass down (certainly, on balance, more useful than harmful), and current thinking (or at least as of a few years ago, when I heard about this) is that the lightning-rod function is at least part of it.

And yet, I think, the operational phrase there is "part of it".  While multiple genetic expressions are likely used to maintain mission-critical functions, for redundancy's sake, if an organism can derive multiple useful functions from a single region (perhaps overlapping in function with differing alternate mechanisms, elsewhere) combines both resilience and the potential to develop new and useful mutations without losing old ones.  Barring the "make use of errors" part, which is rarely good in computer data, consider it equivalent to a RAID0+1 striping-and-mirroring scheme for your server disc-set...


(And, I also forgot to say, DNA wraps up when not in use (unlike enzymes, which are proteins that wrap up in a mysterious way to be in use), so 'internal' bits of DNA aren't inaccessible, particularly, at least not when it counts.  But, if I understand the statement that led to this detail properly, someone is thinking that particular base-combos act as "pre-creased" bits of DNA that help direct the wrapping-up process... But I might be misunderstanding that part.  It's new to me, and I might have the wrong end of the wrong stick.)

[LordBaal]

I'm not really sure this is connected to space anymore.

Radiation damage.

That might affect our (possibly jewish) slaves building the moon piramyds for the space pharaoh.

[jaked122]

I know a way to deal with radiation damage!


I forgot about it earlier, but now I remember. Our genes can carry information, encoding basically anything, right?(Just so long as it doesn't transcribe into RNA and turn into protein, that'd be bad).


We can use Reed-Solomon encoding to store a massively self-correcting chromosome that contains the original information, encoded such that it may be correctly reassembled even if most of the pieces are broken. We can build an organelle for this, like deinococcus radiodurans, and before doing anything with it, we reassemble from this backup, which is more reliable than the original, and then once we reassemble the main genetic copy, we can reencode it repair the damage accrued to the reed-solomon store.

[origamiscienceguy]

What is the dangerous radiation belt around the earth? Van Halen belt? Anyways, we can get past it easily, it is donut-shaped so we can go over or under it I think.

[jaked122]

I think that they ended up just braving it for the apollo programs because they passed through it quickly enough that it didn't matter.


Building a station there though, that's something we'd need to  avoid. Why would we do that though?

[origamiscienceguy]

I think that they ended up just braving it for the apollo programs because they passed through it quickly enough that it didn't matter.


Building a station there though, that's something we'd need to  avoid. Why would we do that though?

I know that the Apollo missions were at about 30% inclination, so they would have gone over most of it.

[Culise]

What is the dangerous radiation belt around the earth? Van Halen belt? Anyways, we can get past it easily, it is donut-shaped so we can go over or under it I think.

Pfft.  You just made me imagine a massive body of songs from these folk orbiting the Earth.  Van Allen belts.  Yes, theoretically you can bypass the Van Allen belts entirely by going through the north or south magnetic poles.  This, however, is ridiculously fuel-inefficient.  If you launch from there, leaving aside the surface logistics of an Antarctic space launch facility, you lose most of the benefits of near-equatorial launches, which is the use of the Earth's own rotation as a sort of "booster" to save on fuel.  A polar transfer is not especially cheap fuel-wise, either.  Finally, you can still transit the Van Allen belts while still avoiding the worst of it; to elaborate on jaked's statement, the Apollo missions were planned on a trajectory to avoid the inner belts and only transited the outer belts, and most of the radiation received was actually from solar radiation once they left the Earth's magnetosphere entirely.  As noted, there isn't too much of a need to station humans within the belts on a long-term basis.  This actually brings up the major issue, though: the question of radiation damage is much more general than the Van Allen belts alone. 

That said, there's apparently a hypothetical project to drain the Van Allen belts by literally using conductive tethers to fly through it like a giant ground wire, which would also have the benefit of power generation until they succeed in their mission objective.  So, there is that...

[Sheb]

If you want to see extreme rad resistance, you guys should check out rotifers. The little bugger can be exposed to doses of several hundred grays (At this stage, their DNA is cut in pieces averaging 500 bp) and survive like ti was nothing.

[Morrigi]

I'm not really sure this is connected to space anymore.

Radiation damage.

That might affect our (possibly jewish) slaves building the moon piramyds for the space pharaoh.

But slaves were never actually used to build the Egyptian pyramids.

[Culise]

Silly Morrigi, these are moon pyramids, not Egyptian pyramids, and a space pharaoh rather than an Earth one.  They can use as many slaves as they wish.

[Reelya]

Yeah, pyramid building was almost certainly a way to channel everyone's labour into a community effort. Similar to how a war effort brings people together and stops dissent, probably. At the time of the pyramid building Egypt really didn't have a lot of outside enemies, so it makes sense they focused on keeping people busy. In the later period where Egypt was actually going out and conquering other places (thus getting a lot of slaves) they didn't build any of the large structures. In other words the conquest and empire took the place of the megaprojects, rather than providing labour for megaprojects.