Twenty is Plenty
Many of us may not realize it yet, but in recent years there has been a dramatic shift in thinking about nature on the part of some cell biologists. Indeed even traditional biotechnology is nothing compared to these new frontiers. In the past, over the millennia, people have wondered about nature and increasingly have applied themselves to finding out how it worked. Once we had some insights, not surprisingly, attempts were made to manipulate nature for mankind’s benefit. Thus we have progressed beyond plant and animal breeding to the insertion of specific pieces of genetic information into target organisms. Some observers have questioned the ethics of these approaches, but the objectives were mainly practical, not philosophically driven.
Since the turn of the new millennium however, accounts have appeared of an entirely new approach to living organisms. Certain scientists, consciously it seems, have set out to upset the created order with a view (they hope) to drive evolution into entirely new and unanticipated directions. The worrying aspect of these studies is not the mythical prospect for “evolution” but the lack of respect for the created order of nature. In view of the existence of a universal genetic code (DNA) directing the life activities of all living cells, some scientists consider it a challenge to change and expand that universal code! Similarly, all living cells make use only of twenty amino acids (out of many other possible choices) in the construction of the proteins that provide the structure and functions of life. Despite this universal condition in nature, these scientists have set out to modify living creatures so that they contain novel or new amino acids. The end objective of all this is to produce organisms with entirely new characteristics. On this issue one commentator asks rhetorically: “if the constraints of the genetic code are indeed history, what constraints remain?” (Economist February 16/02 p. 74) That indeed is the question. If these scientists do not even respect the universal condition of all living organisms, will they respect anything at all? In that they are ignoring the handiwork of the Creator, what could possibly restrict the activities of these people?
Many of the scientists involved in these new techniques are based at the Scripps Research Institute in La Jolla, California. The immediate situation facing these researchers is that there is almost no scope for adding code for new amino acids to the DNA molecule. The four nucleotide bases (in combinations of three) have the capacity to code for 64 molecules. We calculate that number from four taken to the third power or four times four times four, for a total of sixty four. While there are only twenty amino acids, most are coded by more than one triplet combination (three nucleotides). This redundancy reduces the possibility that a single error will result in the wrong amino acid being inserted into a protein. In this way 61 of the 64 possible triplets are already used for the twenty natural amino acids. That leaves only three codons and these signal “stop” for the building of a protein. Rather than churning out endlessly larger molecules, the building of each protein ends at a stop codon.
One American team chose to use a stop codon to code for a new amino acid. This was no easy strategy. To do this they had to produce a new transfer RNA molecule (tRNA). The blue print for a protein is like a succession of key holes strung together and called messenger RNA. What is needed to carry out the instructions on the blue print is something like vertical bricks (tRNA) with a key on the upper end and an amino acid on the lower surface. As the key fits into the appropriate slot of the blue print, the amino acid (on the lower side of the brick) below joins itself to a preceding amino acid in a developing sequence which lies parallel to the blue print chain above. Thus to insert their unnatural amino acid into the protein chain, the Americans formed a tRNA which matched, on the one end, the stop codon already there in the blue print. On the other end (of the brick) they attached their novel amino acid. Thus everywhere this stop codon appeared in the blue print, the novel amino acid was inserted by means of the new tRNA. The Americans were able to do this with living cells of the bacterium Escherichia coli (E. coli). At first, the scientists had to supply the new amino acid to these cells. Eventually however, by more traditional bioengineering techniques, they spliced into the organisms three new genes from a Streptomyces bacterium. In this way they enabled the E. coli cells to manufacture the new amino acid.
This whole process indeed “took some doing.” Nothing about the process could be called spontaneous or even technically easy. Nevertheless these bacteria look perfectly ordinary. Lead scientists Ryan Mehl claims that the whole process indicates that evolution could have achieved this result. Why it did not, he has no idea.
The above technique obviously has very limited potential as all 64 codons are actually in use already. Japanese scientists chose a more difficult approach. They set out to build a pair of new nucleotide bases. Whereas all organisms have four nucleotide bases, the combinations of which allow for 64 triplets, a new organism with six nucleotide bases would have instead the possibility for 216 triplet combinations (six times six times six). This would allow for an awful lot more amino acids! With such modified DNA, the Japanese (and also Americans) have managed to produce new proteins from a suitable soup of chemicals in a test tube. Nevertheless the process is extremely difficult to make work even in a test tube. Moreover when the technique is tried with living cells, they promptly die. The scientists however are optimistic that progress is being made toward success with living cells.
Despite the technical difficulty of these projects, the scientists involved believe that they have demonstrated the potential of evolution to yield astonishing new organisms and products. On the contrary of course, they have yet again demonstrated the irreducible complexity of the living cell. A simple change in the genetic code yields nothing until numerous other metabolic machines in the cell are also modified. The secular scientists may ponder these new challenges but it is the creation based scientist who better understands the situation.
While secular scientists wonder why only four nucleotide bases are used to code for the proteins so necessary to the living cell, creation based Werner Gitt suggests that this choice is optimal from an engineering standpoint (see In the Beginning was Information p. 94). Dr. Gitt declares that this choice allows for the most compact nucleus in the cell and for the most efficient implementing mechanism. Indeed a larger number of nucleotides would not only require much more storage space, but the potential for copying errors would also be much greater. Indeed the elegant simplicity of the genetic code and the associated restricted choices for the amino acids in cellular proteins — both testify to the work of the Designer. Thus we do not fear future “evolution” from this research, but we do fear the “anything goes” attitude which drives these projects.
M. J. Masters
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