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When proteins are made from the information in DNA, a working RNA copy of the gene is made for use by ribosomes, the protein factories of the cell. Therefore RNA, like DNA, stores genetic information, and, like proteins, it also performs chemical reactions.
Bringing RNA into the picture solves the chicken and egg problem. RNA can be both chicken and egg.
What this means to evolutionary biologists is that life could well have BEGUN with organisms made largely of RNA.
This idea of an 'RNA world' has been debated since the 1960's, but Cech and Altman's discovery has convinced most scientists that it is at least possible.
It is now known that RNA is at the heart of many of the basic functions in the cell, and probably evolved in the RNA world. [/b]
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However, this is not always so. Rather, those organisms that leave the most offspring behind, simple or complex, do best. Greater complexity is sometimes a consequence of evolution, but simplification can also be a winning strategy -- it all depends on the environment.[/b]