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Rna Paper

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Ribonucleic acid (RNA) now lives in the shadow of its better known counterpart DNA, but what many people may not realize is that the whole origin of life has been hypothesized to be based on the chemical properties of RNA.

Earth formed approximately 4.6 billion years ago. There was nothing living and the conditions could not have supported life as it is today. A billion years later the earth was covered with some type of algae. In that billion years the first cell was formed, the first bacteria came about, and life began to evolve.

The theory of natural selection is generally accepted by the scientific community at this point in time. The theory states that individuals with traits that make it more fit to survive and reproduce in the world have a better chance of passing on their beneficial trait to their offspring. The offspring will then pass the trait on to their offspring and so on. As the trait is passed on it becomes more common in the population. The theory of natural selection can be used to back track the process of the evolution of life.

There are many aspects of life today that are seen in every classification of life. Proteins are used to do cellular work, DNA or RNA is the genetic material of the cell, and organic compounds are the building blocks for all living things. Because living organisms all share these traits, it has been hypothesized by scientists that there was one original common ancestor that all life came from. This ancestor was a cell.

This original cell somehow had to form from the wasteland that was earth 4 billion years ago. It needed amino acids and nucleotides. Today there are no nucleotides or amino acids just floating around, but 4 billion years ago the conditions were much different and Stanley Miller proved that the formation of nucleotides and amino acids was possible by creating a simulation of what Earth's conditions were like in the time of the first cells.

These amino acids and nucleotides could then have been encased in lipid bubbles to form the first microbes. In these microbes the nucleotides would have reacted with each other to form strands of DNA and RNA. These bubbles could have been the first proto-cells.

The first cell needed a way of storing its genetic information and passing it on to its offspring. RNA was a very likely candidate for the job. RNA is more stable than DNA, and it is hypothesized that RNA could carry out self replication. RNA could have been used as a catalyst on the early Earth. RNA acted like an enzyme and was able to copy other strands of RNA using energy stored in a chemical with three phosphate groups, much like ATP today.

Today it has been hypothesized that ribosomes, the protein factories of the cell, use RNA to catalyze the replication reactions not the proteins in ribosomes. This further proves that RNA can be used as an enzyme catalyst.

RNA's versatility makes it a very possible chemical for life to have started with. It can store information and exist as an enzyme in the form of a ribozyme. The RNA world hypothesis seems very plausible although there are many flaws in the idea. If there were oligonucleotides floating freely in the primordial soup/pudding/jell-o then the compliment strands would have formed with out a problem. The problem with the hypothesis is how the compliment could then be split from the template and complimented again to get a copy of the original template. It seems that with some more research and as more creative ideas come about the RNA world may become as prominent a theory as natural selection.

Since all of life is based on the evolution of cells, DNA, and RNA, it would also make sense that life be classified based on the genetic similarities of organisms, and the genetic similarities of life's ancestors.

Up until about forty years ago the only way life could be classified was by the physical characteristics easily perceived by humans. Then in the 1960's scientists started to figure out how to analyze DNA and good construct phylogenetic trees based on the similarities organisms shared in their genetic material.

Carl Woese then took analyzing the nucleic acids in living organisms to an even more precise level and analyzed the ribosomal RNA to classify organisms. His new process of classification did prove much of the old system true, but it also helped prove the endosymbiont hypothesis. The endosymbiont hypothesis is that early prokaryotic cells lost their cells walls and started folding in on themselves to form a nucleus. They also started engulfing other cells. They may have engulfed mitochondria-like bacteria that instead of digesting, they developed a symbiotic relationship with the other cell. The same happened with chloroplast-like bacteria. The ribosomal RNA in mitochondria and chloroplasts was analyzed and further proof was found for the endosymbiont hypothesis.

Woese then started analyzing bacteria and realized that the two domain classification system based on eukaryotic and prokaryotic cells was no longer plausible. The system had to be split into three parts because Woese found that there were certain bacteria that were as different from other prokaryotes as the prokaryotes are from eukaryotes. By analyzing the ribosomal RNA he realized there must



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