DNA. What do you know about it? You probably know that it codes for our genes. It is unique to each species and each individual within that species. It’s a molecule that looks like a twisty staircase. You might even know what it stands for- deoxyribonucleic acid. And you would be right about all of this. These are the basics of DNA. But lets get our hands a little dirtier.
The “rails” of the twisty staircase are the structural foundation for DNA, but the steps of the staircase are what’s really important. There are four different kinds of “steps.” A step may be one of four molecular bases- adenine, guanine, cytocine, or thymine (commonly represented by A, G, C, T). A gene is made up of about 3000 bases, with A, G, C, and T appearing in different orders. The order in which the A, G, C, and T appear define the gene. Humans have about 30,000 genes. Do the math, and that’s a frickin ton of DNA. That’s not even counting the trash DNA that doesn’t code for genes- which is quite a lot.
And what makes it even more marvelous is that it is universal. All earthly life- from bacteria, to plants, to fungi, to sea sponges, to vertebrates- is DNA-based. Not only are they all DNA based, but the language in which the DNA is coded is the same across life. “ATTTGCCAGATTACAAT” codes for the same thing in a bacterium as it does in a rose bush, as it does in you. That’s why we can put the genes for human insulin into a bacterium and we get… well, human insulin.
Point is, DNA is a highly complex molecule whose processes are just as complex. The DNA system has been evolving since life began, making it one of the oldest and arguably most intricate biological coordinations of structure and function in existence. Earthly existence, that is…
Wouldn’t it be something to take a look at how an extraterrestrial life system works? Assuming that this extraterrestrial species reproduces and traits are inherited across generations, there must be some system by which these traits are inherited. It’s hard to think outside of the DNA box, but let’s try. Maybe they have genetic material that is arranged in something other than a double helix- like a sphere or something. Does it have a structural component and then the genetic message woven in like ours? Does it use similar molecules or ones that we’ve never even seen before? Is 100% of it functional, or are there portions that are trash and just left over from evolutionary past (let me refer you to the name of the blog here!)? The questions and possibilities are endless.
As remarkable as it would be to discover a completely new system of genetic inheritance, I can’t help but hope that it’s not all that different from our own. What a tribute it would be to our humble deoxyribonucleic acid to find that it is a product of the same evolutionary forces felt by lifesystems throughout the cosmos. It’s a romantic notion, really. I like the thought of being related to ET through a shared biomechanism that evolved multiple times, light years apart. It will truly make you feel “one with the universe.”
Unless these extraterrestrials are like the terrifying ones from Alien. Then I think I’ll keep my DNA queries to myself. But even then, it might still be worth being eaten to find out.
Claire,
ReplyDeleteYour blogs always make me think and I've actually thought about this before. In my opinion the organism could realistically only be RNA or DNA based. It really depends on selective pressures and how long it (he or she?) has been around. There's a widely accepted theory that RNA is original "language" of life. As you know, the biggest dogma in biology is that DNA -> RNA -> Protein. Proteins are absolutely necessary and play a HUGE role in everything we do, they catalyze reactions. But what was there before proteins? The scientific community is inclined to lean towards RNA because RNA has catalytic capabilities. Even ribosomes are made up of catalytic RNA. There are tons more of reasons that I don't want to get to on here but the evidence is very convincing. They think that some years later, we started shifting towards DNA because it is much more stable than RNA. Again, I could write novels about all of this but I’ll just leave it at that.
The hardest thing to really wrap my mind around is that we exist because of things that just happen "automatically", based on the rules of chemistry and physics. So if their planet followed a different set of rules, than perhaps it could've evolved differently. But on our planet DNA just makes sense, the molecule is extremely stable in that conformation. There are actually tons of other conformations it exists in that they have created in vitro and some exist in vivo but predominately it exists how you said earlier.
Another question to ask would be is it carbon based? Does it use oxygen and phosphorus like we do? Our crust contains loads more silicon than carbon, why are we carbon based? I wish I could remember right now but there was some kind of chemical selective pressure to favor carbon instead of silicon. Something about bonds maybe. But it is quite possible that they didn’t have those unique selective pressures and they are indeed silicon based instead. Do they use phosphorus like we do? Phosphate groups are the backbone of our DNA. They also activate proteins and play a huge role in our cell’s metabolism. ATP (adenosine triphosphate) powers transporters essential for life. I’ve linked an interesting article at the bottom that talks about how researchers have coaxed a bacterium into incorporating arsenic into their DNA instead of phosphate. Arsenic is chemically very similar to phosphate but is extremely unstable (or so chemists though), that’s why it’s so dangerous to us. Anyways, it basically had no access to phosphate and started incorporating arsenic everywhere instead of phosphate.
I think this is proof that the laws of chemistry are NOT final and that there can be all kinds of organisms out there. NASA is always searching for another planet that has water to even begin looking for signs of life because here on earth every living thing needs water. Are we really so naïve to think that just because our world needs water, their world needs water too? Is it not possible that their metabolism has evolved totally differently in their galaxy and that water is not a vital resource? For all we know, water could be waste to them.
http://www.wired.com/wiredscience/2010/12/nasa-finds-arsenic-life-form/
excuse the typos
ReplyDeleteDaniel-
ReplyDeleteI had heard of the arsenic DNA before but never took the time to try and understand it. How cool! The chemistry behind biology is more plastic than we thought, it seems.
I agree with you- it is a bit egocentric to assume that other life systems follow our rules. But, if there are planets that are similar to ours (and there are probably many), it would statistically make sense that there is at least one that has evolved RNA, and maybe DNA, also. Or something very similar.
You know way more about the chemistry behind all of this than I do, and I think you should write that novel! Or maybe a little article that breaks some of it down for non-science people that could be a guest feature on a certain little blog I know of.... :)