The Myth of The Perfect Genome

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Most of us in modern times know that DNA makes up the biological blueprints for life. Genome is the word for all of a person’s DNA. Unfortunately, sometimes a person’s DNA includes instructions that cause disease. There is a popular idea that this problem is a result of mutations taking us away from having a “perfect” genome. This idea of a perfect genome goes along well with some readings of the Bible that would conclude humans were created perfect and without disease at some point. Since that time we are supposedly getting worse and more diseased, somehow due to sin. But there is a big problem with this idea of a perfect genome: it is a complete myth. There is no such thing as perfect biology.

Perfection vs. Optimization

Consider how you would design a car. What is the perfect car? Maybe a so-called “perfect” car would have all of the things we want most. It might be super fast,¬† have great handling, high acceleration, be cheap to buy, have super high gas mileage, a great sound-system, etc. All the bells and whistles. But can we actually build that car?

In reality, we can’t. If we want high acceleration and speed, we have to give up some gas mileage benefits. If we want low cost, we probably have to give up some of the sound-system. In order to get any benefit we need to give up some of a different benefit; everything is a trade-off. It’s important to note here that this is not a result of sin in any meaningful way. Instead, it’s just a logical consequence of not having infinite power and resources at our disposal.

That doesn’t mean that we can’t get cars we are very happy with. The car I drive is “perfect” for me in the sense that it’s everything I need it to be, but for a person with different needs it would be a pretty awful car. “Optimal” is a far more accurate word for describing my car than “perfect.” An optimal car may not have the infinite power and resources to do literally anything, but an optimal car balances getting me the most possible things I need from it with the trade-offs that are available to me. I don’t have a super fast car, but I don’t need to go fast. I don’t have a lot of money, so I happily trade off high speed for low cost.

“Perfect” really isn’t an accurate word to describe cars or biology. “Optimal” is a far better word. “Perfect” often carries the idea of goodness or rightness in some moral or spiritual sense that can certainly appeal to a religious perspective of the world. But physics knows no perfection, it knows only optimization.

The Optimal Genome

Cars make a relatively simple example, but how about genetics? If we are healthy, it may be easy to think of ourselves as being “perfect” genetically. But genetic change is not deviation from some perfection. In biology we see the same concept as we saw in cars: there is no perfect genome, only an optimal genome for a particular situation.

Consider the allele (version of a gene) that causes Sickle Cell Anemia. Ordinarily our red blood cells are a nice round shape with a dip in the middle, almost like a doughnut with a hole not quite punched all the way through. But in someone who carries two copies (homozygous) of the Sickle Cell mutation, red blood cells tend to get all misshapen and clog up blood vessels. This is both painful and life-threatening, so the Sickle Cell mutation is not too optimal right?

. Some normal and sickle red blood cells. Photo by OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148180
Some normal and sickle red blood cells. Photo by OpenStax College – Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30148180

Wrong. The Sickle Cell mutation isn’t all bad, it’s just a trade-off that most of us here in North America don’t need. People who have one copy of the Sickle Cell mutation don’t get the bad effects of the Sickle Cell allele, but they do get a natural resistance to malaria. This means that in places like Africa where malaria is common, carrying one copy of the Sickle Cell mutation gives you a pretty great benefit. The only risk is if you have kids with someone else who carries the gene then each child you have has a 25% chance of suffering from Sickle Cell Anemia. Malaria is deadly, so in areas where malaria is common, the benefits can outweigh the costs. People in malaria heavy regions are more likely to carry at least one copy of the Sickle Cell mutation

Shaed areas show how common the Sickle Cell allele is in climates where malaria is common. Photo by Muntuwandi at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2932857
Shaded areas show how common the Sickle Cell allele is in climates where malaria is common. Photo by Muntuwandi at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2932857

On the other hand, here in North America, the Sickle Cell mutation offers no benefit and only a cost. An optimal genome here is not the same as an optimal genome in Africa. The forces of evolution are constantly shaping what genes are common in a population, so the Sickle Cell allele is far more common in people in places like Africa than here in North America. Over time, populations evolve to get rid of strictly harmful mutations completely. Evolution knows no perfect genome, but is an efficient optimizer. Optimization through evolution  is the reality that we see in the modern study of genetics.

So No Perfect Genome?

In light of all of the above, there really can’t be such a thing as a perfect genome. What contributes to health in one situation will always contribute to disease in another. A “perfect” genome is like a square circle: just nonsense.

However, there is something to the spirit behind the myth. From a Christian perspective, we see that God describes creation as “good” in the early chapters of Genesis. Life should be good, we think. A life created by following an optimized blueprint is the best life to be had for a limited creature. Certainly not everyone’s DNA is optimal, and not every life is as healthy and good as we would hope. But I don’t think the Christian hope lies in having been created perfect in some way, but rather in being sustained, redeemed, and renewed by a good God who is perfect in every way.

 

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