Age estimation from blood has immediate forensic application

Nov 22, 2010

In principle, the new profiling method could be put to immediate practical use by law enforcement, according to the researchers who report their findings in the November 23rd issue of Current Biology, a Cell Press publication. They have already begun the required validation of the test, which is designed to assure that quality standards are met.

"We demonstrate that human age can be estimated from blood with reasonable accuracy using a simple, robust, and sensitive test assay," said Manfred Kayser of the Erasmus MC University Medical Center Rotterdam in the Netherlands. "Our method is applicable in situations where only bloodstains are available, which covers a large proportion of crime cases."

The method will be especially useful in forensic cases in which age information is important to provide investigative leads for finding unknown persons, Kayser added. Existing methods for age estimation have limited use for crime scene investigation because they depend on the availability of teeth, bones, or other identifiable body parts having physical features that allow age estimation by conventional methods.

Other proposed genetic or biochemical methods to estimate age from blood samples have suffered from low accuracy and technical problems, Kayser said. The new method takes advantage of a fundamental characteristic of known as T cells.

play a key role in recognizing foreign invaders, an ability that depends on a diversity of T cell receptors, each matching specific molecules (antigens) derived from bacteria, viruses, parasites, or aberrant cells such as . That diversity of receptors is achieved through a specific rearrangement of the T cells' DNA, a process that produces small circular as a by-product. The number of those circular DNA molecules (known as signal joint TCR excision circles, or sj TRECs for short) declines at a constant rate with age.

"With our test assay, we quantify the amount of sjTRECs in the total DNA extracted from a small blood sample and use a reference gene not affected by age to compensate for the total amount of DNA in the sample," Kayser explained.

The approach allows accurate estimation of , give or take nine years, the researchers report, suggesting that it would be highly accurate in placing unknown persons into generational categories spanning about 20 years.

Kayser said that the test currently has the highest accuracy of any test designed to estimate a phenotypic human trait from DNA information. Notably, its prediction accuracies are comparable to or better than those recently demonstrated for predicting brown versus blue eye color from DNA, a test that has already been put to forensic use.

These new tests are harbingers of what's to come as researchers uncover new methods designed to reconstruct the appearance of unknown persons from biological crime scene samples or remains. The hope is that such methods will ultimately mean more crimes solved, the researchers say.

"Conventional DNA profiling applied in forensics can only identify persons already known to the investigating bodies, because the approach is completely comparative," Kayser said. "Hence, every forensic lab is confronted with cases where the DNA profile obtained from the evidence material does not match that of any known suspect tested, nor anybody in the criminal DNA database, and such cases therefore cannot be solved so far. In such cases, it is expected that appearance information estimated from evidence material will help in finding unknown persons."

Explore further: York's anti-malarial plant given Chinese approval

More information:

Related Stories

Show me your DNA and I'll tell you your eye color

Mar 09, 2009

More and more information is being gathered about how human genes influence medically relevant traits, such as the propensity to develop a certain disease. The ultimate goal is to predict whether or not a given trait will ...

New genes involved in human eye color identified

May 06, 2010

Three new genetic loci have been identified with involvement in subtle and quantitative variation of human eye colour. The study, led by Manfred Kayser of the Erasmus University Medical Center Rotterdam, ...

Recommended for you

How an RNA gene silences a whole chromosome

7 hours ago

Researchers at Caltech have discovered how an abundant class of RNA genes, called long non-coding RNAs (lncRNAs, pronounced link RNAs) can regulate key genes. By studying an important lncRNA, called Xist, ...

Single cells seen in unprecedented detail

9 hours ago

Researchers have developed a large-scale sequencing technique called Genome and Transcriptome Sequencing (G&T-seq) that reveals, simultaneously, the unique genome sequence of a single cell and the activity ...

York's anti-malarial plant given Chinese approval

Apr 24, 2015

A new hybrid plant used in anti-malarial drug production, developed by scientists at the University of York's Centre for Novel Agricultural Products (CNAP), is now registered as a new variety in China.

The appeal of being anti-GMO

Apr 24, 2015

A team of Belgian philosophers and plant biotechnologists have turned to cognitive science to explain why opposition to genetically modified organisms (GMOs) has become so widespread, despite positive contributions ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.