Identical Twin Genes Are Not Identical

January 12, 2012 by staff 

Identical Twin Genes Are Not Identical, About a year ago I posted the first article in this series, asking whether recent advances in genomics made any difference to the Judeo-Christian notion of humanity being made in the ‘image of God’. That article focused on DNA sequencing data from our closest relatives. This article will focus on the issue of genetic determinism.

Theologians have spent many centuries mining the rich vein of the ‘image of God’ metaphor. Central to the idea is humanity with spiritual capabilities and responsibilities, equipped for moral decision-making and a relationally rich life in community. Historically, the idea has contributed to the conviction that each human individual has an absolute value, independent of their ethnicity, educational level, health status or income.

Do recent advances in genomics threaten or support such a view of humankind, or are they just neutral? Irrespective of one’s belief in God, or not, this is of more than passing interest. Imagine the poor person wrestling for years with the great questions of life and finally deciding to become an atheist, only to then be informed that a cognitive bias derived from his particular set of genetic variants made that decision pretty much inevitable anyway. Such news might be equally unsettling for the person who had just struggled to faith following years of agnosticism. Our deepest human feelings are closely connected with the idea that we choose our own path through life.

The flourishing of genomics in the early part of the 21st century has certainly conveyed the message to many that one’s destiny is written into one’s genome. Whereas scientists are generally scrupulously careful not to give the impression that there is any such entity as a “gene for” some human trait, by the time the latest discovery appears in the media, such caution is often thrown to the winds. The past year has seen the trumpeting of a “gene for happiness,” a “kindness gene” and a “believer gene.” It is not even a question of education, but “genes are to decide” if you are a “caring person.” Genetic testing websites assure us that “your genes are a road-map to better health,” and we all know that road-maps are fixed. Small wonder that there is a creeping genetic fatalism around that subverts the idea of personal responsibility.

Fatalism in itself impacts on human behavior. Studies have shown that subjects exposed to the writings of authority figures doubting free-will are then more likely to cheat. Conversely, workers convinced of the reality of free-will are rated higher in the work-place than those whose beliefs tend more towards determinism.

The reality is that recent genetics research has continued to move steadily away from any notion of genetic fatalism, highlighting the sheer complexity of the genome, and providing some fascinating examples of the ways in which our choices impact upon our own genomes. There is no gene “for” any complex human trait because in fact genes encode proteins or other types of information-containing molecules, and thousands of genes collaborate together during human development in interaction with the environment to generate the unique human individual that each person represents. Those requiring an introduction for the non-specialist are referred to “The Language of Genetics.”

Epigenetics adds further layers of variation and complexity. This refers to the chemical modifications of the DNA that cause genes to be switched on or off. It is such epigenetic modifications that generate the 220 specialized tissues of our bodies. Such acquired changes can even be inherited across several generations, certainly in plants and animals, and maybe in humans as well. In choosing to smoke, drink in excess, or take drugs, we also choose to modify our genomes.

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