It is easy to get excited or frightened about the predictive powers of DNA phenotyping, depending on your perspective. Knowing what genes led to higher intelligence and athletic ability was the first step towards the designer babies of GATTACA. Is this knowledge worth having given the potential for misuse? Going to such extremes with genetic selection makes for a captivating movie, but it can lead to a flawed understanding of the science. The reality of DNA phenotyping is not so scary.
How does DNA phenotyping work?
DNA phenotyping is our attempt at replicating what our bodies do naturally: translating DNA into our physical appearances. It is an attempt because there is rarely a direct correlation between a single gene and a single physical feature. Forensic scientists are currently focusing on determining facial features. Much of our understanding has been gleaned from whole genome studies where scientists compare data from over 7,000 points on participants’ faces to sections of their DNA that contain single nucleotide polymorphisms (SNPs)—that is, sections of DNA that differ by a single letter of the genetic code. Comparing facial maps to genes allows scientists to calculate the probability of physical traits based on the presence of particular SNPs. Predictive algorithms are then used to render an image of a face based on those probabilities.
There is one question that really matters to most people: how well does this all work?
What can DNA phenotyping currently predict?
- Eye color – 77 genes identified
- Hair color – 32 genes identified
- Skin color – 31 genes identified
Dr. Manfred Kayser neatly summarized the specific genes and their corresponding references in a single table from his 2015 paper. These three pigment traits are a good start, but they are a far cry from generating an accurate image of a face. Determining ethnicity is currently accurate at broader levels like European, African and so on. Dr. David Ballard has more to say in this video: Continue reading “The Reality of DNA Phenotyping”