Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.
I'll quote from now on. I just came here to seek possible answers to questions concerning our origins. I need clarification. What is accepted scientific explanation? I've heard strong and credible scientist propose all kinds of theories but they range from DNA occurring from a chemical reaction caused by commentary gases coalescent with Earth, to repressive proteins that would normally obstruct replication, but somehow gave rise to areas in replication that created new strands. I'm not into religion but I have a sneaking suspicion that perhaps there are more complex answers seldom visited, but equally plausible. DNA requires RNA and proteins, but proteins also require RNA and DNA . There's also something else I'm wondering about: Genetic markers show (seemingly) irrelevant - 'junk' DNA, held over from previous evolutionary changes or adaptations - the thing that I don't understand is that alterations in DNA are almost always fatal. We are so genetically different from Neanderthal that we couldn't have produced offspring with them, and the fossil record shows that they abruptly ceased and Cromagdon was introduced, rapidly - much too rapidly for the known chronological scale of development required for evolution. What I've been taught since high school is that there was some anomaly resident to the proteins and RNA that ignited self replication – but again, any changes to genetic architectures are usually fatal to the organism. It's as if everything I think of in explanation is paradoxical, hence negated by what (or which) came first. Sorry to ask so much. By the way, these questions aren't challenges, I'm sincere and I'm just wondering if you or someone else could give me some insight.
It likely was protein that came first, as it's a more simple structure, but I'm not going to recap the whole thread (nobody wants that).
The experiment you're describing specifically (the Miller-Urey experiment of gases in the atmosphere) is no longer the "dominant" theory, but it shares the same basis as the current one: that amino acids necessary for life formed from components and conditions already found on Earth at that time. No one (at least not from any theory I've ever heard) has posited that DNA or RNA suddenly formed before amino acids, or anything of the sort.
Proteins don't require DNA and RNA, they could potentially just form from amino acids, which can form from their component bases. However RNA may have arisen, it doens't have to be a circular paradox with DNA.
And you're providing the explanation to your question right along with it. The changes to genetic architecture are usually fatal; that means not always. It's exactly the same along with evolution. Most mutations aren't expressed, and of the ones that are the results are often irrelevant or crippling or fatal. But the ones that work spread into a population, because they benefit the organism. So no matter how many fatal changes there may have been, it only would take one change that worked to create a new mechanism.
As for the 'junk' DNA, it's not necessarily a holdover from previous generations. It's called a teleomer, and it's non-coding DNA, essentially it does nothing. Every time that DNA is replicated, it cuts off a small amount of DNA on the teleomer, slowly moving towards the coding DNA at the top of the strand. As long as there is DNA on the teleomer it's fine, but once you run out of it you start to lose coding DNA, and some proteins suddenly stop being produced. So it does serve a purpose, just not the same purpose as the rest of your DNA.
I'm not 100% sure specifically what you mean about the Cromagdon, could you clarify this?
I hope I helped with some of your questions. Oh and one minor thing, could you break up your posts a bit, so it's not just one huge lump of text?
Not Much to add to what Khaly said, but ...
There is nodefinitive conclusion on how life appeared on earth, you can read the thread on abiogenesis in this forum for more detail. But the RNA world seem definitely to have the lead for the most likely. Until a more convincing hypothesis come out, of course.
I guess Cromagdon stand for Cro-Magnon. As far as I know (but I am not a specialist of human paleontlogy) they are 2 branches of the human family. And Cro=magnon, our ancestor, wiped out the neanderthal. Why? who knows...
Junk DNA is definitely a misnomer, we don't know why it's here, but it may not be such a junk. Telomere are a good example but account for only a part of its role. Other roles have also been suggested such as spacer between genes allowing a regulation of expression.
As for the danger of mutation, the neutralist theory was suggesting that most of the mutation are indeed silent. not fatal, and even if this theory is loosing its appeal, this still stand true. And some other work suggest that some chaperone proteins could buffer some of the more significant mutations (not the stop one though, but the one changing proteins structure). This allow some interesting speculation about a molecular mechanism for punctuated equilibrium too.
Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
I put this question to my lecturer and we were lost in this topic for nearly 2 hours. We also could not decide which actually came first since one requires the other for formation. We just came to the conclusion that, initially there was a giant pool or chemicals from which simpler stuff like amino acids, sugar molecules etc were formed with the help of some processes. maybe lightning or something, then the next simpler one RNA and then DNA and proteins.
We also came to another interesting solution that proteins came first. From the great pool already discussed, enzymes were formed which were required for various process like transcription, translation, replication and maybe reverse transcription. And according to someone (I do not remember) all enzymes are proteins, and so thus proteins came first.
Either way we hopelessly contradicted ourselves and we decided it was not important what came first, and it ended there.
Lot good things told here...
'which came first?' even if we know it , we be rarely applying or using it except our test on evolution topic! BUT the process of finding out answer, even if much slow, would give many intellectual insights and lot of knowledge about "the earth earlier" & these qualities and knowlede is not only useful in predicting future but also in any field which requires intelligent thought as getting answer to this question is a really a great exersise to out tinanimous brains!!!
But finding the past seems "the exersize unending" because there is always a yesterday to a yesterday ...i.e. yesterday always lies there behind...
when you guys keep on saying protein came first, do you mean peptide chains? Cause a fully functional protein has to fold with the tertiary structures. Only a few simple proteins will just form on their own. The complex enzymes usually need other enzymes and chaperone proteins and perhaps a working ER to do this.
The reason behind RNA being the first is because RNA can also form into ribozymes, simple enzymes that can catalyze peptide synthesis.
I have been thinking about this thing too.. In a biochemistry course we must write an essay about which one of these three came first. The essay should be 2 sides of a A4 paper, not longer than that.. It's just hard to think what to write. Our instructions say there is no wrong or no right answer. But as I just said it's still hard to know what to write and where to start from.. Any ideas? Maybe I find some ideas by reading through this thread?
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