Identification of Unique Mutations in Hair Proteins Suggests Proteins Can Be Used for Forensic Profiling

Source: Lawrence Livermore National Laboratory’s
Forensic Science Center
Researchers at Lawrence Livermore National Laboratory hypothesize that scientists will eventually be able to analyze variation in individual hair protein sequences to determine who is responsible for a crime. Their hope stems from their successful extraction of mutations, random gene alterations, from human hair older than 250 years old.
The researchers revealed in a detailed scientific paper published by the Public Library of Science that they managed to find protein markers, mutations in protein sequences that aid in identification, from 82 living and recovered hair samples for the first time. Every individual had a specific as well as different number and pattern of hair protein markers. Thus, protein analysis could join DNA analysis as a key technique in exonerating and identifying suspects.

Protein identification is superior to DNA identification because proteins persist

According to Lawrence Livermore National Laboratory's overview on the experiment, protein samples are more reliable than DNA samples because proteins are more chemically robust or durable. DNA often degrades due to environmental conditions like light and heat, breaking down so much that even DNA amplification won't help with recovery. On the other hand, proteins last longer. Scientists proved that proteins are advantageous in terms of durability by using skeletal remains that are hundreds of years old.

Proteins are small biological compounds formed by chains of amino acids, the basic building blocks of organic life. Like DNA, proteins are often unique and specific to one person. DNA includes the genetic instructions for creating proteins. Therefore, a DNA mutation can lead to a mutation in a single amino acid, creating single amino acid polymorphisms (SAPs).

Scientists will use the protein markers they identified to map out an individual's protein pattern

Source: Lawrence Livermore National
Laboratory’s Forensic Science Center
The researchers at the lab used hair samples from 76 living people and 6 skeletal remains, carefully studying the samples' protein markers. They analyzed the sequences in 185 protein markers from 66 European Americans, 5 African Americans, 5 Kenyans, and 6 skeletal remains from London. According to the laboratory, the protein markers all had somewhat unique combinations. Although they only identified 185 protein markers, the Lawrence Livermore National Laboratory believes there are up to 1,000 individual protein markers that can be used to differentiate one individual from another. Currently, the researchers know enough protein markers to map out an individual's protein pattern and identify one person from a population of approximately 1 million.

Methods of forensic profiling have rapidly evolved from visual comparisons to detailed sampling

The steady development of protein-based identification mirrors that of DNA profiling. 1933 marked the first time a person was convicted based on DNA. Forensic profiling, which was once based on visual comparisons using the naked eye, has gained a lot of attention. Scientists are now capable of extracting DNA samples from the seemingly impossibly minuscule, including invisible skin cells.

Very recently, invention of new forensic science techniques has moved towards hair proteonomics, study of the genes produced by hair. Protein mutations, like the ones discovered in the hair samples, occur because DNA mutations also lightly impact amino acids, which construct proteins. Analyzing protein mutations in hair could supersede and end the controversial use of hair strand comparisons, marking the end of an era in forensic science's focus on visual comparisons. Future scientists may analyze skin cells, teeth, and bones because those also have protein markers.

News media and other scientists have expressed excitement over a new forensic profiling tool

The news has been met with great fervor, leading to an article from The Washington Post pondering the possibility that analysis of hair proteins will replace the prominent use of DNA analysis in criminal investigations. Overall, the new discovery is a possible "game-changer" according to Christopher J. Hopkins, a forensic science director at University of California at Davis. However, he also noted, "there are steps to go before this new technique will be able to reach its full potential." Jessica Yin, a writer for the blog Information 3.0 asked fellow students interested in biology about why the discovery could be a game-changer.

Organizations dedicated to combating wrongful convictions support protein identification

One proponent of new forensic profiling techniques is Glinda S. Cooper, director of the Innocence Project, a famous non-profit organization established with the sole purpose of helping wrongly convicted victims. The famous program, which has successfully exonerated 344 inmates thanks to DNA evidence, identifies outdated and subjective forensic techniques -- including bite mark and hair comparisons -- as a primary reason for wrongful accusations. 

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