Friday, May 9, 2014

An artificial genetic code

The natural DNA alphabet consists
of A (adenine), T (thymine), C
(cytosine), and G (guanine).
Image source.
As reported in Nature yesterday, scientists were able to add a third pair of bases to the DNA of a living organism.  Naturally, news sources sensationalized the study with misleading headlines, such as “Scientists Engineer First Living Organism with an Expanded Genetic Alphabet.”  Many headlines make it sound as if a new form of life was created in a laboratory.  This is not at all the case.  No life was created in a lab.  So, what did this study actually do?

Background

DNA is composed of a series of molecules called ‘nucleotides’ (or, more specifically, deoxyribonucleotides) strung together in a twisted ladder-like form.  Each nucleotide consists of a phosphate group, a sugar molecule, and a nitrogenous base.  The bases form the rungs of the ladder, while the phosphate groups and sugar molecules form the sides.  DNA has four bases: adenine, thymine, cytosine, and guanine, abbreviated as A, T, C, and G.  The bases are paired so that the two sides of the ladder are like negative images of each other.  A is always paired with T, and C is always paired with G.  The order of these bases along the DNA molecule determines the genetic code, which a cell reads as plans to produce proteins essential for life.  All organisms use the same genetic alphabet of these four letters (though in some cases, such as in RNA, thymine can be replaced by another base, uracil).

The study

In the latest experiment, scientists at the Scripps Research Institute introduced a third base pair into a bacterium.  The new bases, referred to as d5SICS and dNaM, apparently closely resemble the guanine-cytosine pair.  The new bases themselves were not a novelty in this study; these and other artificial bases have been introduced to DNA molecules previously.  However, the Scripps researchers seem to be the first to successfully implant the modified DNA into a living cell, which then replicated it.

I should emphasize that the synthetic DNA did not actually introduce any new information to the cell.  The natural DNA code works because each set of three natural nucleotides corresponds to a particular amino acid, which is a component of proteins.  The new bases do not correspond to any amino acid, so the cell has no way of reading them.  The bacterium can only copy the DNA as written, provided enough d5SICS and dNaM.  The cell was able to continue living unabated because the modified DNA was on a plasmid, not on the crucial chromosomal DNA.  Plasmids are distinct rings of DNA that can be freely changed and even exchanged with other individuals.  Genetic engineering frequently takes advantage of plasmids, and this study was no exception.

While I have not yet seen anyone attempt to use this study as an argument against intelligent design, I wanted to clear up any misconceptions that might result from a cursory view of the news headlines.  Some may argue that, because alternative letters are available for the genetic alphabet, the fact that all organisms use the same alphabet is a testament to common ancestry.  However, the scientists in this study had great difficulty incorporating the synthetic bases into the genome, and there are hints that they may not be quite as stable as the natural bases.

In principle, this study had very little, if anything, to do with the origin of life.  Rather, the researchers hope that the success of this experiment will lead to further advancements in bioengineering, such as making bacterial strains that can synthesize a wide variety of artificial materials.  This concept may seem like “playing God” to some people, but I do not see it as such.  We are not creating new life, nor can we.  That ability is limited to God alone.  The idea that man can assemble bare molecules into a new form of life smacks of materialistic thinking, for life is nothing but an assemblage of molecules in such a view.  I see genetic modification of bacteria to be no different than domesticating and training dogs.  We are free to utilize nature and subject it to our will for our own purposes, but we cannot forget that it is a gift from the One who created us.  We are stewards of His creation, nothing more.

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