It is known that the human genome consists of four “letters”. They are conventionally designated as A, C, G and T. That is, the human genome is completely composed of four types of molecules - adenine, cytosine, guanine and thymine. A greater number of chromosomes in the genes is not evidence of greater development. It only speaks of the number of threats and shocks through which one or another biological species managed to pass. What information is contained in DNA and using what methods it became possible to decipher the contents of the human genome?
Genetic research objectives
Complete genome sequencing allows you to read all the sequences of these “letters”. It allows you to identify unknown genes and make medical therapy as effective as possible. That is why one of the most popular medical services (of course, among those who can afford it) is sequencing. Diabetes, malignant tumors and heart diseases - a predisposition to these diseases allows you to identify the DNA decryption procedure. Based on the predictions received, a person has the opportunity to adjust his lifestyle and reduce adverse environmental factors. Therefore, some researchers are convinced that complete genome sequencing should be included in the set of mandatory studies of newborns.
Project history
The genome decoding project was launched back in the early 90s. In order for a complete decoding of the genome to take place, it took about a dozen and a half years. This scientific project brought together scientists from various countries - China, Germany, France, Japan. At the beginning of the new millennium, Bill Clinton and Tony Blair officially announced that the “draft” of the genome was completed. In 2006, Nature published information that the sequence of the last chromosome was obtained. Exome sequencing has also appeared on the genetic services market - the process of identifying damaged areas in a DNA molecule. Society believed it was on the verge of a new era.
What is sequencing?
Sequencing is the final step in the analysis of the human genome. Before this, the following stages follow: material is selected and cloned. And also there is a preliminary testing of a DNA site with simpler methods. Sequencing is the final definition of the nucleotide sequence of a DNA molecule. In total, there are two methods for this genetic study: firstly, the Maxam-Gilbert method is used. It is based on methods for cleaving a DNA molecule on one base. There is an easier way, which is used more often in practice. This is the so-called dideoxy method, or Sanger sequencing.
Sanger genome decoding stages
The latter method includes the following stages of the study:
- the studied DNA fragment is hybridized with a primer;
- enzymatic synthesis of the molecule occurs;
- in the next stage, the material is subjected to electrophoresis;
- and, finally, the results are analyzed by geneticists on a radio autograph.
Most of these devices are capable of recognizing up to 300 bands in a DNA molecule.
Sanger DNA Decryption Process
The original sequencing method that scientists were able to use to process genomes was Sanger sequencing. Its essence is as follows: DNA is cloned, and then the resulting mixture is divided into four parts. Each of them is placed in a special solution in which the following substances are present:
- DNA polymerase molecules;
- primers that facilitate the replication process;
- a mixture of four copies of nucleotides;
- individual variations of one of the nucleotides.
Thus, the decoding of the genome according to Sanger is almost identical to the process of cloning human DNA. These processes differ only in that false components are mixed into the nucleotides.
Decryption process today
Now the Sanger sequencing method is fully automated. It is carried out on special equipment - these machines are called sequencers. Chemical reactions are carried out in one test tube. The results obtained as a result of decoding by Sanger are analyzed using computer technology. Modern sequencers can “read” information from 600-1000 nucleotides at a time. With automation, the sequencing process is now much faster than before.
Will it be available?
Now the leading countries that produce DNA sequencing are China and the United States of America. They are in a competitive situation - the country that will be the first to decipher the human genome, having spent less than a hundred dollars on it, will win. An American research company called Ilumina is China’s main adversary on this issue. Back in 2010, Chinese scientists purchased first-class equipment, which allowed them to occupy all these years the leading position in the market for genome sequencing services. But, firstly, these devices began to inevitably become obsolete, and, secondly, the DNA decryption service is becoming more and more cheap. Now China does not want to spend the already missing financial resources on equipment from abroad - scientists decided to develop their own equipment. Whoever wins the battle for leadership will show the future. But today, the decoding of the genome in some cases costs no more than 600 dollars.
Is gene decoding really useful?
However, not everything is so simple in this matter. Some researchers insist that gene sequencing is not so much beneficial as harmful. Can this process really give something to an individual individual or be a contribution to science? Why are some specialists more than critical about DNA decryption?
The fact is that sequencing methods, from their point of view, are nothing more than an ultramodern method of fortune telling on coffee grounds. The person is responsible for obtaining information about his genome. Different motives push people to answer questions about their DNA. Someone seeks in this way to better know themselves. Someone is trying to protect themselves from diseases - and is doing everything to be safe. However, this approach can be extremely negative.
For example, people who find out that they have a risk of getting cancer, later on suffer from serious depression and run to the doctors endlessly. And this despite the fact that even complete sequencing gives results that predict the development of terrible diseases with a risk of 50%. However, a wave of hysteria is spreading more and more among the clients of these services. All this led to the fact that some authorities, for example, in the United States, took seriously the restriction of the activities of medical companies.
Genetic passport - yes or no?
In the domestic environment, the expression “genetic passport” is more popular. But, as often happens, science could not predict all the consequences of its achievements. Indeed, the decoding of “letters” does not yet guarantee that the written “words” will be correctly understood. For example, genetics still cannot unambiguously answer the question of how many genes are contained in the human genome. It used to be that this amount ranged from 10 thousand to 40 thousand. Now researchers are speculating that this number ranges from 10 to 25 thousand. It is impossible to say more precisely. And genome sequencing is just one example of how a scientific discovery causes even more unanswered questions.
The cost of decoding the genome is now about 1 thousand dollars. However, reading genes for many is only a source of additional stress. For their own money, customers get such results, from which they then can not fall asleep at night. Sequencing is a study that involves obtaining information about various genes. Including the “genetic passport” includes genes that are involved in the development of various diseases - diabetes, obesity, cardiovascular disease. You do not need to be an international class geneticist to understand: there may be genetic prerequisites for these diseases, however, the lifestyle that a person leads plays a significant role.
Possible mistakes
Now many scientists point to the fact that mistakes can often be avoided during sequencing. Moreover, their probability is measured not in tenths, but in whole percent. Their occurrence is associated with the features of decryption technology. Sequencing is a process that can be compared to making a copy of a huge film several thousand frames long. At the same time, it is allowed to make copies that will be no more than 20 frames long. To make them as accurate as possible, they are removed "with a margin" so that additional segments overlap each other. Decoding the human genome is still more difficult - because the length of the human chromosome is tens and hundreds of billions of letters. The task of collecting the human genome was quite ambitious for many countries. However, only one conclusion can be drawn now - the genome is assembled with a large number of errors. Perhaps in the future, scientists will be able to collect data more accurately. And today we need to put up with this situation.