Sequencing is ... Segmenting by Sanger

It is known that the human genome consists of four "letters". They are conditionally designated as A, C, G and T. That is, the human genome is completely composed of molecules of four types - adenine, cytosine, guanine and thymine. The greater number of chromosomes in the genes is not evidence of greater development. It only talks about the number of threats and shocks through which one or another biological species managed to pass. What information is contained in the DNA and by what methods is it possible to decipher the contents of the human genome?

Objectives of Genetic Research

Complete sequencing of the genome 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 disease - a predisposition to these diseases can reveal the procedure for decoding DNA. Based on the predictions received, a person has the opportunity to adjust his lifestyle, reduce adverse environmental factors. Therefore, some researchers are convinced that the full sequencing of the genome should be part of the compulsory research of newborns.

History of the project

The project for decoding the genome was launched in the early 90's. In order for the complete decoding of the genome to occur, it took about fifteen years. This scientific project has united around itself scientists from different 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 had been completed. In 2006, the publishing house Nature published information that the sequence of the last chromosome was obtained. Also on the market of genetic services appeared the sequencing of exome - the process of determining the damaged areas in the DNA molecule. The society believed that it was on the threshold of a new era.

What is sequencing?

Sequencing is the final step in the analysis of the human genome. Before this, there are following stages: the material is selected and cloned. And also preliminary testing of a site of DNA by more simple methods occurs. Sequencing is the final determination of the nucleotide sequence of a DNA molecule. In general, there are two ways of this genetic study: first, the Maxam-Gilbert method is used. It is based on the methods of splitting a DNA molecule on a single base. There is an easier way, which in practice is used more often. This is the so-called dideoxy method, or sequencing by Sanger.

The stages of decoding the genome by Sanger

The latter method includes the following stages of research:

• The studied fragment of the DNA molecule hybridizes with the primer;
• An enzymatic synthesis of the molecule takes place;
• The next step 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 the DNA molecule.

The process of decoding DNA by Sanger

The initial method of sequencing, which scientists could use to process genomes, was sequencing by Sanger (Sanger sequencing). The essence of it 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 contribute to the replication process;
• A mixture of four copies of nucleotides;
• Individual variations of this from nucleotides.

Thus, the decoding of the genome by Sanger is almost identical with the process of cloning human DNA. These processes differ only in that the false components are mixed into nucleotides.

The decoding process today

Now the Sanger sequencing method is completely automated. It is carried out on special equipment - these machines are called sequencers. Chemical reactions are carried out in a single tube. The results obtained as a result of the Sanger interpretation are analyzed using computer technology. Modern sequencers can "read" information from 600-1000 nucleotides simultaneously. With the help of automation, the sequencing process is now much faster than before.

Will it be affordable?

Now the leading countries that produce DNA sequencing are China and the United States of America. They are in a situation of competition - the country that will be able to decipher the human genome first, having spent less than a hundred dollars on it, will win. An American research company called Ilumina is China's main opponent in this matter. Chinese scientists in 2010 bought first-class equipment, which allowed them to occupy the leading positions in the market for genome sequencing services over the years. But, firstly, these devices have become inevitably obsolete, and, secondly, the service for decryption of DNA is becoming more and more cheap. Now China does not want to spend already lacking financial means for equipment from abroad - scientists decided to develop their own equipment. Who will win in the battle for leadership - will show the future. But already today the decoding of the genome in some cases costs no more than 600 dollars.

Is the decoding of genes useful?

However, not everything is so simple in this matter. Some researchers insist that the sequencing of genes does not bring so much benefit as harm. Can this process really give something to an individual or be a contribution to science? Why do some specialists refer to the decoding of DNA more than critically?

The fact is that the methods of sequencing, from their point of view, are nothing more than an ultramodern way of guessing on the coffee grounds. Responsibility for obtaining information about his genome is borne by man himself. Different motives push people to answer questions about their DNA. Someone strives in this way to know himself better. Someone tries to protect themselves against diseases - and does everything to be safe. However, this approach can be extremely negative.

For example, people who learn that they have a risk of getting oncology, later begin to suffer from serious depressions and run around the doctors endlessly. And this despite the fact that even full sequencing gives results that predict the development of terrible diseases with a risk of 50%. However, among the clients of these services, a wave of hysteria is spreading more and more. All this has led to the fact that some authorities, for example, in the United States, have seriously set about limiting 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. After all, deciphering the "letters" does not yet guarantee that the written "words" will be correctly understood. For example, genetics still can not unequivocally answer the question of how many genes are contained in the human genome. Previously it was believed that this number ranges from 10 thousand to 40 thousand. Now researchers suggest that this number ranges from 10 to 25 thousand. More precisely, it is impossible to say. And the sequencing of the genome is just one example of how scientific discovery is causing more and more unanswered questions.

The cost of decoding the genome is now about 1 thousand dollars. However, reading the genes for many is only a source of additional stress. For their own money, clients receive such results, which then can not fall asleep at night. Sequencing is a study that involves getting information about different genes. Including in the "genetic passport" includes genes that take part in the development of various diseases - diabetes, obesity, cardiovascular diseases. You do not need to be an international geneteer to understand: the gene prerequisites may be to these diseases, but the way of life that a person leads, plays a significant role.

Possible mistakes

Now, many scientists point to the fact that errors can often be avoided during sequencing. And their probability is measured not by tenths of a percentage, but by whole percentages. Their appearance is connected with the peculiarities of the decryption technology. Sequencing is a process that can be compared to making a copy of a huge film with a length of several thousand frames. It is allowed to make copies, which will not be longer than 20 frames. To make them as accurate as possible, they are removed "with a margin", so that additional segments overlap each other. With the decoding of 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 assembling the human genome was quite ambitious for many countries. However, only one conclusion can be drawn now: the genome is collected with a large number of errors. Perhaps in the future, scientists will be able to collect data more accurately. And today it is necessary to put up with this situation.