DNA is in danger
Why the disclosure of serial murders upset Americans
Tatiana Pichugina
The method of DNA analysis is so widely used in modern criminology that it has actually completely replaced biochemical and serological blood tests. With the help of DNA tests, long-standing serial murders were uncovered, the authenticity of the remains of the royal family was confirmed, suicide bombers were identified. The other day, the prosecutor's office of the Sverdlovsk region announced its readiness to exhume the remains of the dead tourists of the Dyatlov group, if necessary. About the possibilities of DNA examination – in the material of RIA Novosti.
Criminal Code
Human DNA consists of three billion nucleotides – organic compounds sequentially linked to each other. There are four types of them in total, denoted by the letters A, G, C, T. It is not for nothing that the genome is compared with the text.
In 1985, English geneticist Alec Jeffries published a series of articles in Nature describing a method for distinguishing people by DNA. He found that in different parts of the chromosomes, the same short sequence of nucleotides (minisatellite) is repeated many times, unrelated to any of the proteins – in fact, garbage.
Jeffries marked this "garbage" in the entire genome with radionuclides and made an X-ray. It turned out that the pattern formed by these mini-satellite inserts is unique for each person. The only exception is identical twins. So the genetic analogue of the "fingerprint" was discovered.
The scientist used this method to recognize kinship, establish paternity and identity of twins. A year later, using DNA, the police identified the man who raped and killed two girls in Leicestershire. To do this, we had to check the DNA of five and a half thousand local men.
An X-ray showing the first genetic "fingerprint" prepared by Alec Jeffries at the University of Leicester on September 19, 1984. © Science Museum.
Useful "garbage"
Since then, genetic fingerprinting has been used everywhere in criminology. The method used by Jeffries has been replaced by advanced technologies that give a more accurate result in the shortest possible time. But it is still based on the analysis of nonsensical ("garbage") DNA sections – short tandem repeats, or STR markers.
In such a section, a "word", for example, of three nucleotides CAG can be repeated from three to twenty times. It is not necessary to sequence the DNA completely, it is enough to analyze ten to fifteen sites in different chromosomes and count the repeats in each of them. The list of STR marker lengths is made up of a unique human genotype.
After collecting DNA traces at the crime scene, criminologists transfer them to the molecular genetic laboratory. The results are compared with samples taken from suspects.
It is possible to establish that two DNA samples – from the crime scene and from the suspect – belong to the same person with almost one hundred percent accuracy (99 and a dozen nines after the decimal point).
The advantage of the method is also that very little material is required: literally a couple of dozen cells. A few drops of blood, traces of saliva on a glass or semen on clothes are enough. DNA is a very stable molecule that persists in tissues and in the form of traces for decades. And it is possible to extract it from the buried bone remains after tens of thousands of years, which is used by archaeologists in the reconstruction of the pre-written history of mankind.
Amateur genealogy helps catch maniacs
Since 2009, Law No. 242 "On State Genomic Registration in the Russian Federation" has been in force, according to which citizens convicted of serious and especially serious crimes, including sexual ones, must undergo this procedure. Their genotypes are stored in the database of the Ministry of Internal Affairs. DNA data of unidentified persons obtained by the investigation from the crime scene is also placed there.
At the same time, information is being accumulated about the genotypes of individuals and populations of people in scientific institutes and firms performing DNA analysis for research purposes and on a commercial basis. Last year in the United States, such databases contributed to the disclosure of three long-standing serial murders.
To establish the identity of the "killer from the Golden State", who has about fifty rapes and twelve murders on his account, investigators conducted a search on the public database GEDmatch, where ordinary people load their genotypes to find close relatives or build a family tree. Forty years later, the suspect was arrested, he turned out to be Joseph James Deangelo, a former cop.
Despite the impressive success, these and two other investigations conducted in a similar way caused discontent in American society. How legally did the police use public DNA databases to search for criminals, is this an invasion of privacy?
The other day, Bennett Greenspan, founder of FamilyTreeDNA, a firm that performs commercial DNA analysis orders for clients from around the world, retroactively admitted that he provided the FBI with a database and was forced to justify himself through an email newsletter.
World-class expertise
In 1988, Pavel Ivanov, a young employee of the V. A. Engelhardt Institute of Molecular Biology of the USSR Academy of Sciences, performed a molecular genetic examination, and this helped to catch the "Ivanovo maniac" Sopov. This is how domestic DNA forensics was born.
In 1993, under the leadership of Pavel Ivanov (now he is deputy director of the State Center for Forensic Medical Examination of the Ministry of Health of Russia), the remains of Nicholas II and his family, shot in 1918 in Yekaterinburg, were identified. The victims of natural and man–made disasters and terrorist attacks were identified - after the tsunami in Thailand in 2004, at the Sayano-Shushenskaya hydroelectric power station in 2009, during the crash of the Sukhoi Superjet aircraft in May 2012 and the explosion of an airliner from Sharm el-Sheikh in 2015.
In 2012, Pavel Ivanov and his colleagues examined the DNA of the Palestinian leader Yasser Arafat, who died in 2004, and established the authenticity of his belongings, which were then sent to laboratories in different countries to determine the cause of death.
For the future
DNA analysis can work, even if the circle of suspects is not initially defined. So, in 2011, genetic signs of a suicide bomber who detonated a bomb at Domodedovo airport were revealed, according to which scientists of the N. I. Vavilov Institute of General Genetics of the Russian Academy of Sciences established the ethnicity of the criminal, speeding up the identification of his identity.
This became possible thanks to population-genetic databases, where the genetic profiles of the population are presented. The set and frequency of occurrence of markers in the DNA of representatives of some peoples differ. Both the length of STR markers and the replacement of individual letter nucleotides inside them (SNP variants) are analyzed.
So far, we have been talking about DNA located in the nucleus of a cell in the form of chromosomes. But there, in the cell, there is another kind of DNA – inside independent cellular organoids, mitochondria. There are dozens and hundreds of them in the cage. They undergo chemical reactions with the release of energy necessary for the whole organism.
Mitochondria's own DNA is a small molecule in the form of a ring with a small number of nucleotides compared to chromosomal DNA. It is also used in criminology for identification. According to it, the pedigree on the maternal line is restored, because it is inherited only by a female child from the mother.
So far, the dream remains to create a portrait of a suspect based on DNA. Several genes and their combinations are responsible for external signs, such as eye color, hair, forehead, nose shape. In exceptional cases, this information can be useful for finding a person, but now this direction is at the level of scientific research.
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