The first genetic studies date back to the 19th century, long before we knew what genes were . By growing peas ( Pisum sativum ) with different characteristics, the Augustinian monk Gregor Mendel was able to elaborate the so-called laws of inheritance, which describe how some characters are transmitted between successive generations. At the same time chromosomes were discovered, and later the DNA molecule.
In 1953 the researchers Watson and Crick described the structure of DNA as a double helix, a finding for which they received the Nobel Prize together with Maurice Wilkins. The study of genes continued to advance at an ever faster pace, culminating in the complete sequencing of the human genome in the early 2000s . In this article we will explain in detail what this scientific advance consisted of and its implications.
Origins of genetic sequencing
The genome is the set of genes of an organism or species. These are encoded in DNA, which is made up of four types of subunits, called nitrogenous bases. The nitrogenous bases of DNA are adenine, thymine, cytosine, and guanine. Each DNA sequence that codes for a protein is called a gene. Knowing the complete DNA sequence of an organism is important for several reasons that we will discuss below.
The first DNA sequencing techniques date back to the 1970s. Frederick Sanger received his second Nobel Prize for developing a technique called dideoxynucleotide sequencing, which allowed the partial replication of DNA sequences in such a way that ordering the fragments obtained obtained the nucleotide sequence of the original DNA strand. The first complete sequencing of the genome of an organism was carried out with this technique, identifying the 11 genes of the bacteriophage Phi-X174 in 1977.
What is the human genome project?
The first initiative to sequence the human genome arose at the University of California in 1984. The project grew and recruited scientists from different institutions, until the Human Genome Project was established in 1990 . At first, it was estimated that it would take 15 years of work and 3,000 million dollars to complete the project. The money came from both public funds and private institutions.
The American biologist Craig Venter, founder of the company Celera Genomics, played a relevant role and contributed part of the capital to the project. The different laboratories that participated in the initiative competed to sequence specific chromosome regions, to be the first to contribute the sequences to the project database and thus obtain priority in any subsequent patent registration .
In April 2000 the first draft of the project was published, and in 2001 the journals Nature and Science published the definitive sequence of the human genome , with 99.9% reliability and one year ahead of the originally planned date. Subsequent corrections were made, and in 2006 the project was terminated.
The objectives that were met were two, on the one hand the complete sequencing of the genome and on the other the positioning of the genes corresponding to each of the chromosomes. The DNA samples came from anonymous donors, keeping strict confidentiality, and new tools were created for the genetic study and the storage of this information during the development of the project.
Utility of the Human Genome Project
It is known that many diseases have a genetic origin, so knowing the sequence of each gene and establishing the relationships between these and different diseases is interesting from a biomedical point of view. This makes it possible to improve existing therapies and the development of new ones, as well as to improve early diagnosis before the first symptoms appear.
For example, we now know that Alzheimer’s disease has an incidence risk associated with several genes, located on chromosomes 1, 14, 19 and 21 . Huntington’s disease also has a genetic basis, being related to a single gene located on chromosome 4. Understanding why these genes are expressed and cause the disease will allow finding a treatment and opens the door to its possible cure.
A direct application of human genome sequencing is gene therapy , which consists of inserting functional copies of defective or absent genes in the patient. For example, gene therapy techniques have been used in the treatment of severe combined immunodeficiency, caused by deficiency of the enzyme adenosine deaminase. Treatment consists of removing T lymphocytes from the patient, modifying them to produce the enzyme, and re-implanting them.
Associated ethical issues
The possibility of carrying out genetic modifications in an individual or species raises certain ethical doubts. In the case of gene therapy described above, these considerations do not exist, since the modification carried out does not affect the descendants of the patients receiving the treatment, and said treatment is not different from a tissue transplant from any donor (the advantage is that the existence of a compatible donor is not required).
Another ethical issue is related to the early diagnosis of genetic diseases during pregnancy, as this can lead to the voluntary interruption of pregnancy by the parents. This also raises questions about the right to privacy of genetic information, and the right of the patient to be adequately informed before making a medical decision.
Another issue surrounded by some controversy is the possibility of patenting genes , since the techniques used for their sequencing were subject to patents. On the one hand, UNESCO has positioned itself in favor of the knowledge derived from the Human Genome Project being the patrimony of Humanity. On the other hand, those who contributed private capital to the development of the project, such as Craig Venter through Celera Genomics, argue that without the right to patents and the incentive of an economic benefit, the development of new techniques that allow science to advance would be limited. .
To minimize the impact of these issues, in the 1990s the Legal and Social Ethics Program was established in the US, which sought to study all possible ethical issues that might arise from the sequencing of the human genome and seek an appropriate solution for each one. of the ethical dilemmas encountered. Another function of this program is to educate the general population and professionals about the objectives of the Human Genome Project, as well as its limitations.