DNA phenotyping

Not to be confused with DNA profiling.

DNA phenotyping (fee-no-type-ing) is the process of predicting an organism’s phenotype using only genetic information collected from genotyping or DNA sequencing. This term, also known as molecular photofitting, is primarily used to refer to the prediction of a person’s physical appearance and/or biogeographic ancestry for forensic purposes.

DNA phenotyping uses many of the same scientific methods as those being used for genetically-informed personalized medicine, in which drug responsiveness (pharmacogenomics) and medical outcomes are predicted from a patient’s genetic information. Significant genetic variants associated with a particular trait are discovered using a genome-wide association study (GWAS) approach, in which hundreds of thousands or millions of single-nucleotide polymorphisms (SNPs) are tested for their association with each trait of interest. Predictive modeling is then used to build a mathematical model for making trait predictions about new subjects.

Predicted phenotypes

Biogeographic ancestry determination methods have been highly developed within the genetics community, as it is a key GWAS quality control step.[1] These approaches typically use genome-wide human genetic clustering and/or principal component analysis to compare new subjects to curated individuals with known ancestry, such as the International HapMap Project or the 1000 Genomes Project. Another approach is to assay ancestry informative markers (AIMs), SNPs that vary in frequency between the major human populations.[2]

Beginning in 2009, academic groups developed and reported on predictive models for eye color and, more recently, hair color in the European population.[3] More recently, companies such as Parabon NanoLabs and Identitas have begun offering forensic DNA phenotyping services for U.S. and international law enforcement.

Differences between DNA profiling and DNA phenotyping

Traditional DNA profiling, sometimes referred to as DNA fingerprinting, uses DNA as a biometric identifier. Like an iris scan or fingerprint, a DNA profile can uniquely identify an individual with very high accuracy. For forensic purposes, this means that investigators must have already identified and obtained DNA from a potentially matching individual. DNA phenotyping is used when investigators need to narrow the pool of possible individuals or identify unknown remains by learning about the person’s ancestry and appearance. When the suspected individual is identified, traditional DNA profiling can be used to prove a match, provided there is a reference sample that can be used for comparison.

An early and successful use of forensic DNA phenotyping - the Baton Rouge serial killer

From the late 1990s to the early 2000s, a series of murders were committed in Louisiana. Eyewitness statements and FBI profiling indicated the perpetrator was likely a Caucasian male. After investigators tested DNA samples from thousands of Caucasian males and found no matches with DNA from the crime scenes, DNA phenotyping was performed on a crime scene DNA sample by DNAPrint Genomics. This testing indicated the ancestry of the suspect was 85% sub-Saharan African and 15% Caucasian, pointing to an African-American individual and changing the direction of the investigation. Within two months, police arrested Derrick Todd Lee, who was later convicted for two of these murders.

Published DNA phenotyping composites

See also

References

  1. Tian, C.; Gregersen, P. K.; Seldin, M. F. (208). "Accounting for ancestry: population substructure and genome-wide association studies". Human Molecular Genetics. 17 (R2): R143–50. doi:10.1093/hmg/ddn268.
  2. Shriver, M. D.; Smith, M. W.; Jin, L.; Marcini, A.; Akey, J. M.; Deka, R. & Ferrell, R. E. (1997). "Ethnic-affiliation estimation by use of population-specific DNA markers". American Journal of Human Genetics. 60: 957–964. PMID 9106543.
  3. Liu, F.; van Duijn, K.; Vingerling, J. R.; Hofman, A.; Uitterlinden, A. G.; Janssens, A. C. J. W.; Kayser, M. (2009). "Eye color and the prediction of complex phenotypes from genotypes". Current Biology. 19 (5): R192–3. doi:10.1016/j.cub.2009.01.027. PMID 19278628.
  4. Allocca, Sean (15 January 2015). "First DNA-Phenotyped Image of 'Person of Interest' in Double Homicide". Forensic Magazine.
  5. Cookson, Clive (30 January 2015). "DNA: the next frontier in forensics". Financial Times.
  6. Snow, Kate (30 June 2015). "Putting a Face to DNA: How New Tech Gives Hope in Cold Cases". NBC Nightly News.
  7. Manning, Johnathan (1 September 2015). "CPSO releases sketch based on DNA sample from cold-case murder". KPLC News.
  8. Full article on this in National Geographic, July 2016, page 34.
  9. DeFede, Jim (10 September 2015). "Revolutionary DNA Tech Used to Create 'Serial Creeper' Sketch". CBS Miami.
  10. Rabin, Charles (23 September 2015). "DNA links 'The Creeper' to sex attack on Miami Beach". Miami Herald.
  11. Dacey, Kim (3 February 2016). "Police hope composite image can help close cold case". WBAL.
  12. Glenn, Stacia (6 April 2016). "Tacoma police release composite images of suspects in 1986 slayings". Tacoma News Tribune.
  13. DeWitt, David (6 April 2016). "Police sharpen image of uptown Athens serial rapist, ask public for help identifying". The Athens News.
  14. Robinson, Michael (15 April 2016). "New DNA technique could lead to a break in snowbird murder case". The Star.
  15. Bezaire, Christie (21 April 2016). "Windsor police hope DNA composite profile will help solve 45-year-old murder". CTV News Windsor.
  16. Culver, David (11 May 2016). "Loudoun County Turns to Composite Image Based on DNA to Crack Cold Case". NBC4 News Washington.
  17. Towne, Shaun (16 May 2016). "Police release composite of suspect in unsolved Warwick murder". WPRI 12 News.

External links

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