A new way DNA tech can help you ID your unknown suspect
When Parabon delivers a Snapshot report based on a DNA specimen submitted to them, each phenotype is associated with a measure of confidence
DNA analysis is a wonderful investigative tool. You can match evidence carrying biological trace to the person who left the trace, with near-certainty you have the right guy.
This assumes, of course, that you have an existing DNA profile that matches evidence, one already on a suspect list or that is found in CODIS. If you don’t, DNA evidence is only a little better than a fingerprint. You might be able to get close with a familial match, but mostly you’re still looking for some other connection to the crime. What if your DNA evidence could also show you what the donor looked like?
Parabon NanoLabs (Parabon) now offers a service called Snapshot (officially, the Snapshot DNA Phenotyping System), which can predict the genetic ancestry, eye color, hair color, skin color, freckling, and face shape of the owner of a DNA specimen. Snapshot won’t direct you to the door of your suspect, but it can tell you who you can confidently exclude from your list of ‘possibles.’
A Précis of the Science
Genetics — which is the parent science for forensic DNA analysis — uses the terms genotype and phenotype to identify genetic characteristics. The genotype is the DNA sequence at a particular site in the genome that varies between individuals. The phenotype is the expression of those genetic variants.
Genes almost always occur in pairs. When they don’t, the result is often a birth defect. If you have two identical genes that express a characteristic, you are homozygous for that pair. If the genes are different, you are heterozygous.
For example, there are three varieties of genes that express as the phenotype referred to as blood type: A, B, and O. A homogenous pair of blood type B genes produces the phenotype of type B blood. If a person is heterozygous for those genes, having one B gene and one A gene, they will have blood type AB. If they are heterozygous with one B and one O gene, they will have the phenotype of blood type B again, as the O gene is recessive. A dominant gene paired with a recessive will have the phenotype of the dominant gene.
Many phenotypes are not solely dependent on genes. You can have “tall” genes that normally produce a person of above-average height, but only if they receive proper nourishment as they grow. A malnourished person might wind up at average or below-average height, even if their parents are Rebecca Lobo and Shaquille O’Neal. A trait that is less dependent on the genes that express it has “low heritability.”
There is considerable ongoing dispute about environmentally-determined traits, the “nature vs. nurture” argument (which was the basis for the plot of the movie Trading Places). Even so, some phenotypes, specifically, those that are highly heritable, express reliably, no matter what the conditions are as they mature. For example, your natural hair, eye, and skin tone or color is written in stone (actually, in proteins) at the moment of conception.
Not all DNA codes for a phenotype. Much of the total DNA strand has no known effect on the physical characteristics of the owner.
How the Technology Works
When Parabon delivers a Snapshot report based on a DNA specimen submitted to them, each phenotype is associated with a measure of confidence. A high level of confidence represents a trait unlikely to be affected by upbringing or environment. A low level of confidence tells you the phenotype might be something different.
A Snapshot report also shows excluded traits. These are traits that are highly unlikely to express in the donor, given his genotype. For example, a Snapshot profile might not be able to predict whether a subject has green or hazel eyes, but could say with near-complete confidence that they do not have black or brown eyes.
Research in progress may lead to more physical characteristics predictable through DNA analysis. Height is a complex phenotype dependent on many gene pairs making it more difficult to predict with high accuracy, but Snapshot may be able to predict less complex traits, like hair quality (straight, curly, wavy, kinky), in the near future.
Parabon has many cases under its belt, some of which were tests conducted while the technology was in development. Recently, a homicide case in Columbia (S.C.) http://coladaily.com/2015/01/09/new-technology-produces-image-of-person-of-interest-in-2011-homicide-investigation/ developed new leads through public disclosure of a Snapshot composite.
Ellen Greytak, Ph.D. — Director of Bioinformatics at Parabon NanoLabs — said, “Because traditional DNA analysis is limited to identity matching, and turnaround times are long, DNA evidence is currently used only rarely as an investigative resource. Snapshot changes that; it puts DNA at the top of an investigator’s priority list. This is a completely new way to use DNA.”
There are various factors involved in setting a price tag on a Snapshot analysis, but Greytak estimated the cost at less than $5,000. Typical turnaround time is one month although a rush order (with a premium price) could be completed in under a week under optimum conditions.