Evolution’s fatal problem of non-standard genetic codes


Chances are you’ve heard of the genetic code. This is the code in our DNA that represents the instructions on how to make different proteins (the building blocks of life). A protein is made of a long ‘chain’ of amino acids (of up to 20 types) in a specific sequence, determined by the genetic code in our DNA. Like a fancy piece of origami, this amino acid chain is folded into a specific three-dimensional shape, based partly on the amino acid sequence, but with the help of special ‘chaperone proteins’. So the protein does not typically fold to its most natural ‘relaxed’ equilibrium shape, but to the shape determine by the Creator to fulfil its specific role. 

Fig. 1. The standard genetic code. The three-letter words, such as Cys, Trp, Arg, etc., stand for the 20 different amino acids.

Like all codes, this is a sequence of symbols, like words made up of letters. Our DNA contains four letters, A, T, G, and C. When a protein is to be produced, the instructions for that protein are copied onto a transcript. This transcript is made of a molecule called RNA. RNA also has four letters, but T is replaced with U.

These letters are read in three-letter words called codons. In the genetic code, every codon has a meaning. A codon could refer to a specific amino acid, such as serine, or it could mean ‘stop’ (stop codons mark where the instructions for a protein’s amino acid sequence ends). Fig. 1 shows all the possible codons and their respective meanings in the standard genetic code.

Both evolutionists and creationists have long pointed out that the genetic code is virtually universal. That is, it is virtually the same in all living things (and the code is optimised). Evolutionists see this as evidence for common ancestry, while biblical creationists see this as evidence for common design.

However, the genetic code is not entirely universal: There are at least 33 different genetic codes that have been discovered throughout living things!1 These other codes are very similar to the standard genetic code, but some of the codons have different meanings (DNA is a remarkable language). This is a huge problem for evolutionists, but not for creationists.

To explain why, an analogy may help. Imagine you are programming a robot on how to get through a maze. The instructions you give it are an ordered sequence of directions, either Left, Right, North or South. The robot has a compass to know which directions are North and South. The robot follows the sequence of steps and successfully gets through the maze. Now imagine that there is a second robot that is also programmed to follow the same path through the maze. However, the compass in this robot is pointing in the opposite direction to the compass of the first robot—it is pointing toward South instead of North. This means that every time it reads ‘North’ in the code it will end up travelling South and when it reads ‘South’ in the code it will travel North. Thankfully, a friend of yours goes through the entire set of coded instructions and changes all the Norths to Souths and all the Souths to Norths. Because of this, the second robot is still successfully able to navigate along the correct path through the maze.

It is easy for a programmer to go through a code and swap two words if they swap meanings, but it is impossible for one code to slowly change into the other via a series of small changes over time. If the meaning of ‘North’ and ‘South’ were swapped without the words ‘North’ and ‘South’ being swapped in the coded instructions, the robot would go in the wrong direction every time it reads North or South. What if the programmer then changed all the Norths to Souths and all the Souths to Norths but accidentally missed one North? The robot would successfully navigate the maze until it reads that word North and then it would travel in the wrong direction. It doesn’t matter that all the rest of the instructions are correct—this single incorrect instruction means that the robot would fail to exit the maze.

How this applies to life

The same is true for living cells. In different genetic codes, some codons have different meanings. An example concerns the mitochondria in our cells (the ‘powerhouses’ which provide the cell with energy). These have their own DNA and use a genetic code that is different to the genetic code used in the nucleus of our cells. In the standard genetic code, AGA and AGG both refer to the amino acid arginine. In the vertebrate mitochondrial code (used by our mitochondria), AGA and AGG both mean ‘stop’.

Since evolutionists insist that all life descended from one ancestral organism, in their view all life started off with the same code, and any deviations must have arisen subsequently. So they must believe that at some point in time, AGA and AGG transitioned from meaning ‘arginine’ to meaning ‘stop’.

Impossible step

But how could that possibly be? If the meaning of AGA and AGG were changed to mean ‘stop’, every protein whose manufacturing instructions included the codons AGA or AGG (which formerly meant ‘add arginine to the chain’) would suddenly be truncated. In other words, the production of those proteins would be terminated as soon as the manufacturing machines came across the codons AGA or AGG. This would cause certain death in any living organism.2

Bacteria do not have mitochondria; most evolutionists say that mitochondria started off as separate organisms, such as bacteria. They propose these were ‘swallowed’ by another unicellular organism (fig. 2), and somehow got incorporated as part of that host cell. This is the endosymbiosis theory of how mitochondria evolved. If the code change happened in the host cell after these hypothetical ancestor organisms had become mitochondria, their function would instantly stop. The host cell would die, since it crucially depends on the energy from these tiny factories.

commons.wikimedia.org, Kate Taylorphagocytosis
Fig. 2. Unicellular organisms can ‘swallow’ a food particle (which may be a prey organism) by a process called phagocytosis (= ‘cell eating’). The object is in effect moved to the cell’s interior by being engulfed by the cytoplasm.
The endosymbiotic theory of how mitochondria arose claims that mitochondria started off as free-living ancient organisms that were phagocytosed into another organism. But instead of being digested, they began to cooperate with their predator to mutual advantage.

If an evolutionist should argue that the ancestors of mitochondria had this code difference already before being incorporated, that means the same code transition as discussed above had to have happened in the ancestry of those organisms. We have already seen that this would be impossible, as it would be fatal (see also ‘Anticipating an objection’, below).

It gets worse for evolution

But even if we were to ignore that, and for the sake of argument assume that these ancestors had somehow managed to make the change, evolutionists have a further problem. This is because they argue that after the ancestor of mitochondria was ‘swallowed’, a substantial portion of its DNA (and the genes within that portion) was transported into the host cell’s nucleus, where it became part of the host’s nuclear DNA (discussed in depth here) . This is an integral part of the evidence put forward for the endosymbiotic origin theory. However, if this were the case, the protein manufacturing machinery would not be able to correctly read these genes, since they would be written with a different code.

Evolutionists are very aware of this code change problem. Francis Crick, who, along with James Watson solved the structure of DNA, argued that once the genetic code was in place it would be impossible to change because any changes would be lethal.3 Yet, according to evolutionists, such a lethal event must have happened at least 32 times.

No naturalistic solution in sight

In his famous book, The Greatest Show on Earth, Professor Richard Dawkins said,

Any mutation in the genetic code … would have an instantly catastrophic effect, not just in one place but throughout the whole organism. If any word … changed its meaning, so that it came to specify a different amino acid, just about every protein in the body would instantaneously change … Unlike an ordinary mutation, which might, say, slightly lengthen a leg, shorten a wing or darken an eye, a change in the genetic code would change everything at once, all over the body, and this would spell disaster.4

This would seem to be a fatal problem for evolution, but is not a problem within the biblical creation model. God can easily create an organism with a different genetic code and ensure that its DNA is programmed in such a way as to make sense under those codon meanings. Indeed, in creating life in this way, God has provided a problem for naturalistic attempts to explain life without the Creator—at this very time in history. Thus, scientists who now understand this are more than ever “without excuse” (Romans 1:20) if they deny that God exists.

Anticipating an objection

Evolutionists might point to the fact that the codons AGA and AGG are two of the least used codons in the bacterium E. coli.* So, if the supposed bacterial ancestor of mitochondria likewise also used AGA and AGG much less than other codons, changing the meaning of these codons to mean ‘stop’ would have a much smaller effect than changing the meanings of other codons.

However, they are still used frequently enough for this to cause significant problems. There are over 100 genes in E. coli associated with essential cellular functions that contain an AGA or AGG codon within the first 25 codons.* Because these genes are associated with essential cellular functions, if the meaning of AGA or AGG changed to mean stop, the cell would certainly die.

The fact that these codons are often found near the start of the genes, rather than elsewhere in the genes, is also significant. This means that if their meaning were to change to mean stop, they wouldn’t just slightly shorten the genes, but shorten them substantially. Even if these codons were used only once, towards the start of a single essential gene, changing the meaning to ‘stop’ would still be fatal to the bacterium.

*Chen, T. and Inouye, M., Role of the AGA/AGG codons, the rarest codons in global gene expression in Escherichia coli, Genes and development, 8(21):2641–52, 1994; pubmed.gov.

Published: 11 August 2022

References and notes

  1. Elzanowski, A. and Ostell, J., The genetic codes, NCBI, ncbi.nlm.nih.gov,7 Jan 2019. Return to text.
  2. Tan, C., and Stadler, R., The Stairway to Life, Evorevo Books, p. 48, 2020. Return to text.
  3. Crick, F.H.C., The origin of the genetic code, Journal of Molecular Biology, 38:367–369, 1968. Return to text.
  4. Dawkins, R., The Greatest Show on Earth, Transworld, London, 2009, pp. 409–410. Return to text.

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