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Secrets in the blood

The molecular structure of DNA is shaped like a double spiral.
The molecular structure of DNA is shaped like a double spiral. / R. C
  • DNA tests, which are now 30 years old, can reveal rare illnesses, fathers who didn’t know they had children and unkown ancestors

On 10 September 1984 geneticist Alec Jeffreys had arrived early at his laboratory in Leicester. It was just an ordinary Monday like any other until, just after 9am, he had one of those ‘eureka’ moments which have occurred periodically in the history of science.

Jeffreys was carrying out an experiment in the dark room and he took an X-ray from the developing tank. He looked at the genetic material on the plate and within seconds he realised what he was looking at: the variations in the genetic code of the three people who had taken part in the test (the laboratory technician, his mother and his father) served to identify each of them, with no equivocation. He had found a genetic footprint which makes each person unique.

Since then, this DNA testing technique has proven vital in resolving crimes, identifying rapists and dead bodies, checking would-be immigrants’ claims and proving paternity. Although individuals of the same species share a large part of their DNA sequencing (deoxyribonucleic acid) there are also some highly variable aspects which are unique to them (genetic markers) and these are used for identification purposes.

It is now 30 years since that discovery was used for the first time to demonstrate a parental relationship and the British government accepted the result of a DNA test as evidence. On that occasion the immigration authorities had to admit their mistake after they had refused to let a young man from Ghana into the country, although his mother was living in Britain legally. They doubted that she really was his mother, and suspected that she was actually his aunt. The government asked the scientist for help and the genetic footprints showed that the young man was telling the truth.

Found guilty through DNA

From that moment on, there were so many requests for DNA tests that Alec Jeffrey’s team at the Leicester laboratory couldn’t cope with the workload. “It has gone crazy,” he said at the time.

He collaborated on the first police case which was solved through use of this new technique, known as the Pitchfork Case. DNA testing identified Colin Pitchfork as the man who had raped and murdered two teenage girls. After comparing the samples of semen from the girls’ bodies and a blood sample of a person who was initally detained, it was shown that they did not match and the suspect was innocent. Pitchfork therefore became the first person to be found guilty through DNA evidence.

Since then gigantic steps have been taken in developing this test. It has gone from being a very expensive manual technique which only provided a small amount of very specific information, to an automated process which enables the first complete human genome to be sequenced (together with the genes contained in the chromosomes) something which occurred in 2004 after 13 years of work by an international consortium and a budget of three billion dollars.

“The difference is that nowadays we can read all the fragments which codify the proteins of the 19,000 genes of a person, and instead of taking a decade, it can be done in ten days and costs between 1,000 and 1,500 euros,” says Enrique Samper, the president of NIMGenetics (a biomedical company which specialises in genetic clinical diagnosis), who qualified in Biological Sciences at Michigan State University.

This technological progress and the progressive reduction in the cost of DNA tests has made them available to a large part of the population who, either from lack of knowledge about them or from a lack of resources, would previously have been unable to use them for early diagnosis or to demonstrate a parent-child relationship.

At present there are between 6,000 and 8,000 illnesses (of the 10,000 from which a human can suffer) which have a genetic base and originate from changes to DNA. These can be mutations or changes in the copy number of the genetic fragments which lead to an illness, most of which are classified as ‘rare’.

“Fifteen years ago, with the physical study of the chromosomes (every human cell has 46 chromosomes, half inherited from the father and the other half from the mother) we were able to determine one or two per cent of the causes of genetic illnesses. Nowadays we are approaching 60 per cent. This has made these tests necessary and, at the same time, affordable,” explains Dr Samper. He expects there to be major growth in the sector in the next few years “because different studies show an increase of between 15 and 25 per cent a year in genetic tests.”

Paternity tests are another field in which DNA plays a decisive role. “It is irrefutable. A cigarette end is worth more than 200 witnesses and a million bits of paper,” says Fernando Osuna, a lawyer who specialises in paternity suits and who is known, among other cases, for that of bullfighter Manuel Díaz ‘El Cordobés’. At present he is dealing with over 400 cases of this type and says “they are not all to claim an inheritance.” He believes that when someone embarks on a paternity suit, which can be a long and costly process, “they are also doing it for reasons of dignity, to know who their father is, or also to defend the honour of a mother who may have been disparaged for years.”

In 2015 alone, the National Institute of Toxicology and Forensic Sciences received 1,485 judicial requests for DNA testing to determine parenthood. When data about these tests began to be registered, in 2007, there were only 401.

The samples are kept with extreme care to avoid any type of contamination or irregularity in the testing process. The price of DNA testing by this institute is regulated by the Ministry of Justice: a test of this type costs 600 euros plus IVA if the father, mother and child are analysed, and if somebody else is analysed as well, there is an extra charge of 200 euros.

However, there is no need to go to court to clarify doubts about paternity. By making a simple phone call or filling out a form on the internet people can obtain a kit which produces results that are 99.99 per cent reliable. “The only thing that people have to do at home is take the sample. The analysis is carried out in the laboratory, and is as reliable as the legal validity test,” says Mercedes Alemañ, the manager and technical director of Cefegen, one of the companies which sells these kits. Cefegen currently carries out between 800 and 1,000 paternity tests a year, 50 per cent more than when they began about ten years ago.

A large part of their success is due to their anonymity, but it is also due to their simplicity. “The person requesting the test has to collect oral epithelium cells from the inside of the cheek with a cotton bud and leave it to dry before sending it back to us in the kit we sent them,” says Mercedes Alemañ. In five days and for 199 euros, it will be clear whether or not they are the father.

In the search to know who we are and where we come from, man has found genetics to be his main ally. Whereas people used to rely on relatives’ memories and historical archives to draw up their family tree, it can now constructed from genes. From DNA tests and the enormous genealogical registers, data can be cross-referenced to see whether someone is descended from Julius Caesar or Isabella of Aragon. Private companies, especially in America, offer tests which enable people to look back thousands of years. One of the most popular is 23andMe, located in Silicon Valley, which has DNA data of 1.2 million men and women.

In their case, as well as discovering the regions from which a person originated, it is also possible (with consent) to make contact with unknown parents and even calculate what percentage of the DNA comes from the Neanderthals.

This new service, which is provided by about 20 companies round the world - the most important are Ancestry, Family Tree and MyHeritage- is relatively recent in Spain. The company DNA Solutions, originally from Australia and now with a base in Seville, confirms this trend and the great quantitative leap that occurred in 2015, when demand grew by 70 per cent compared with the previous year.

By analysing certain areas of DNA, they can establish which group of people with similar genetic profiles a person belongs to. They are called haplogroups: there are hundreds of them and they share a common past. Each one is associated with an ancient people (Celts, Vikings or Jews, for example) and geographic areas. The samples can be taken at home with a simple cotton bud. The cost? Between 169 and 299 euros. In just four months, family origins will no longer be a secret.

Non-invasive prenatal tests detect genetic alterations associated with extra copy chromosomes through a simple analysis of a mother’s blood sample.

judicial requests for DNA analysis were received by the National Institute of Toxicology in 2015, to determine parenthood. In 2007, there were only 401.

DNA studies provide crucial information for adapting nutritional and sporting habits to the genetic characteristics of individuals.