I need help debating a Creationist

violator
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I need help debating a Creationist

So I've been debating the whole "where did we come from" thing with a Creationist freind of mine and I've actually come a long way with him. I first succeeded in convincing him that evolution can account for the modern-day diversity of life, even though it can't really explain where the first life came from. So, my Creationist freind filled in this "first life" gap with God, and said that DNA is too complex to form on its own. I then succeded in convincing him that DNA is quite capable of forming without any outside influence. What I'm looking for now, and have had trouble finding, is some info about how DNA that replicates itself could (even hypothetically) lead to cells. If anyone knows anything about this I'd appriciate it, or even a link would help me out.

'The universe we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind pitiless indifference.'
- Richard Dawkins


mr804
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It's very simple,we came

It's very simple,we came from ribbs and dust!


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Okay, here is what I

Okay, here is what I know...

 (I'm a Biology major, but I am only a Freshman still)  This very thing is what really convinced me that there wasn't a god.  The rest of the details (fallicy of the bible, etc) were mere details.  Understanding abiogenesis put the final nail in the coffin for me!

This is very generalized and basic...

 We know how the first cell came about right?  Google the Urey-Miller experiment...get a good basic idea of what went on with that.  Then, you will understand how basic life came from mere chemicals.  Then, you have the basic cell which had very basic DNA (such as bacteria) that the DNA strand was not double helixed yet, but simply a ring.  Blah, blah...some of the bacteria evolved to more complex cells/organisms and the more complex formed double helixes.  Well, DNA replicates itself via RNA.  That's pretty much it.  The cell came first, then the DNA.  Cells replicate themselves two-fold. 2-4-6-8 and so forth.

 Google this: abiogenesis  (the origins of life)

Here are a few links to get a more detailed explanation:

http://www.ncbi.nlm.nih.gov/About/primer/genetics_cell.html

 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookCELL1.html

 

I hope this helps you out! 

 

 

"Chlorinating the Gene Pool"


deludedgod
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I'm not going to suggest to

I'm not going to suggest to you that we know how DNA formed, but we do have some good ideas regarding abiogenesis.

What really is under discussion here is the origin of self-replicating molecules. Once self-replicating molecules are in place, the process of biological evolution as described kicks off. The origin of these molecules is not really of any particular concern to evolutionary biologists, that being the discipline called primordial biochemistry. No theory, after all, explains everything. To evolutionary biology, the existence of such molecules is a priori.

On the other hand, I do have a short series of notes on the matter of the origin of self-replicating molecules, if you are interested.

 The process of formation of organic autocatalysis is time consuming. It begins with Piezoelectric systems on crystallien surfaces, which form the progenitors of ribozymes. The first biological molecules on Earth may have been formed by metal based catalysis on the crystalline surface of minerals.

In principle, an elaborate system of molecular synthesis and breakdown called metabolism could have existed as such long before the first cells. Life requires molecules which catalyze reactions hsih lead directly or indirectly to replication of more molecules like themselves. Catalysts with this self promoting propertycan use raw materials to reproduce themselves and therefore divert the same materials from the production of ther substances. In modern cells the most versatile catalysts are polypeptides. However, they cannot propogate self-replication, they do not replicate. There needs to be a molecule which can act as a catalyst and guide its own replication. Such a molecule does exist: RNA

 Polynucleotides Can Both Store Information and Catalyze Chemical Reactions. RNA can propagate itself by means of complementary base pairing. However, this process without catalysis is slow, error prone and inefficient. Today, such processes are catalyzed by a massive battery of complex interactions of RNA and proteins.

In the RNA world, the RNA molecules themselves would have acted as catalysts. A pre-RNA world probably Predates the RNA One. It is unlikely RNA was the first self-replicating propogater. It is difficult to imagine that they could form through nonenzymatic means. The ribonucleotides are hard to form enzymatically, also RNA polymers entail a 5 to 3 chain which must compete with other linkages that are possible including 2 to 5 and 5 to 5. It has been suggested that RNA was anteceteded by molecules with similar properties, but that were similar. Candidates for pre-RNA include p-RNA and PNA (peptide nucleic acid)

The transition from pre-RNA to RNA would have occurred through the synthesis of RNA via these simpler components as template and catalyst. Laboratory experiments demonstrate this as plausible. PNA can act as a template for RNA molecules. Once the first RNA molecules had been produced, they could have outphased their antecedents leading to the RNA world

Single-Stranded RNA molecules can fold into highly elaborate structures Comparisons between many RNA structures reveal conserved motifs, short structural elements used over and over again as part of larger structures. Common motifs include

Single strands, double strands, single nucleotide bulges, triple nucleotide bulges, hairpin loops, symmetric internal loops, asymmetric internall loops, two stem junction, three stem junctions and four stem junctions. RNA molecules can also form common conserved interactions such as psuedoknots and “kissing hairpins” and hairpin-loop bulge contacts.

-Protein catalysts require a surgace of unique countours. RNA molecules with appropriate folds can also served as enzyme. Many of the ribozymes work by positioning metal ions at the catalytic sites. Relatively few catalytic RNA exist in modern day cells, being the polypeptides work much better.

An example of In vitro selection of synthetic ribozymes:

 

 

-A large pool of dsDNA each with a randomly generated sequence. Transcription and folding into randomly generated RNA molecules. Addition of ATP derivative containing a sulfer in place of oxygen Only a rare RNA has the ability to phosphorylate itself. This is captured by elution of the phosphorylated material

These experiments and others like them have created RNAs that can catalyze a wide variety of reactions:

Peptide bond formation in protein synthesis, RNA cleavage and DNA ligation, DNA cleaving, RNA splicing, RNA polymerization, RNA and DNA phosphorylation, RNA aminoacylation, RAN alkylation, Amide bond formation, amide bond cleavage, glycosidic bond formation and porphyrin metalation, since, like proteins, ribozymes undero allosteric conformation change

Self-Replication Molecules Undergo Natural Selection

-he 3D structure is what gives the ribozyme chemical properties and abilities. Certain polynucleotides therefore will be especially successful at self-replication. Errors inevitably occur in such processes, and therefore variations will occur over time. Consider an RNA molecule that helps catalyze template polymerization, taking any RNA as a template

-This molecule can replicate. It can also promote the replication of other RNA. If some of the other RNA have catalytic activity that help the RNA to survive in other ways, a set of different typers of RNA may evolve into a complex system of mutual cooperation.

One of the crucial events leading to this must have been the development of compartments. A set of mutually beneficial RNA could replicate themselves only if the specialized others were to remain in proximity

Selelection of a set of RNA molecules according to the quality of replication could not occur efficiently until a compartment evolved to contain them and therefore make them available only to the RNA that had generated them. A crude form of this may have simly been simple absorption on surfaces or particles.

The need for more sophisticated containment fulfilled by chemicals with the simple physiochemical properties of ampipathism. The bilayers they form created closed vesicles to make a plasma membrane. In vitro RNA selection experiments produced RNA molecules that can tightly bind to amino acids. The nucleotide sequence of such RNA contains a disproportionate number of codons corresponding to the amino acid. This is not perfect for all amino acids, but it raises the possibility that a limited genetic code could have arised this way. Any RNA that guided the synthesis of a useful polypeptide would have a great advantage.

 

"Physical reality” isn’t some arbitrary demarcation. It is defined in terms of what we can systematically investigate, directly or not, by means of our senses. It is preposterous to assert that the process of systematic scientific reasoning arbitrarily excludes “non-physical explanations” because the very notion of “non-physical explanation” is contradictory.

-Me

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