Russian researchers from Engelhardt Institute of Molecular Biology and Moscow Physics and Technology Institute have developed a biochip, able to establish one’s identity as accurate as 99.6% using only traces of his DNA. This biochip can be very useful for criminal investigations, for instance, in forensic medical examination in order to narrow a circle of suspects or to identify a dead body. Results of this work can be found in Russian scientific magazine “Molecular biology”, volume 44, issue 4.

A biochip contains characteristic DNA sequences of three genes: ABO, AMEL and HLA-DQA1. First gene, ABO, is responsible for human blood group (A, B, AB and O), and has about 90 possible sequence variants. HLA-DQA1 is a gene, located in major histocompatibility complex – it codes a protein, localized on surfaces of B- and T-lymphocytes. This gene has 34 sequence variants. And the last but not the least – AMEL gene encodes a protein, involved into dental enamel development. AMEL gene is located on sex chromosomes; moreover, its sequence on X chromosome slightly differs from its sequence on Y chromosome – this difference helps identifying gender. Analysis of various sequences of these three genes allows dividing humans into 1350 groups with every human being belonging to one of these 1350 groups.

 

 

New technique has promising perspectives in criminal investigations, because blood analysis is not always possible – blood spots may not always be present at a crime scene. Moreover, a blood spot can be too old, too dirty or too small, making traditional analysis impossible. Analysis of a DNA sequence requires much less amount of a sample. For analysis researchers used filter-tipped cigarette buds with traces of suspect’s saliva and crumpled laboratory paper tissues with some sweat left on them. Experiment participants were also told to sip some water from a non-reusable glass, and then researchers collected lip prints from glass’s edge with a tissue with sterile water. All these materials were used for DNA extraction from target genes, and this DNA was then applied to a biochip, which was made on the basis of PAAG (polyacrylamide gel) and contained characteristic DNA sequences of all three genes, required for the analysis.

Donor DNA is labeled with a fluorescent dye, and the group, to which a suspect belongs, is defined according to positions of fluorescent dots on a biochip’s gel. For biochip construction its developers used genetic material or DNA from 422 volunteers. Probability of an accidental coincidence of all three genes in a genotype is quite small – 0.4%, but not small enough to prove involvement to crime commission. Such analysis, though, helps reduce amount of suspects and reconstruct a crime, when several people were involved in an incident and left at crime scene something from which genetic material could be extracted.

Researchers hope that adding more genetic loci than three to their development helps significantly improving test’s information value.

Source: Science & Technologies

Kizilova Anna