The Human Genome Project, one of the 21st most significant breakthrough

The Human Genome Project (HGP) was achieved in 2003 and officially began in 1988 but it takes its roots from the first discoveries concerning genetic sequencing made by two scientists working independently, Walter Gilbert (US) and Frederick Sanger (UK) in the 70s. 

After the sequencing of various viruses and bacterias’ genomes, scientists from 20 institutions and 6 different countries set out the ambitious goal of sequencing the whole human genome counting no less than 3 billion nucleotides. This project’s achievement was mainly due to nanotechnologies, that came along the second technologic revolution, and to the informatics progress. Indeed, assisted by automatons, these precise and efficient tools allowed scientists to simultaneously sequence millions of DNA fragments and to classify them on tiny chips in only a few hours. This major breakthrough had a huge impact on our societies, it revealed a lot of new medical perspectives but also gave rise to many ethical questions.

To sequence the whole human genome, scientists used the chain termination method established by F.Sanger. This method begins by the amplification of the DNA fragments to be sequenced by DNA polymerase. This enzyme then assembles the matching bases to form the strand complementary to the template strand. The primer determines the region of the template DNA that will be sequenced while the terminator base, a fluorescent tagged base also called dideoxynucleotide, marks the end of the transcription. All these replicas are then classified thanks to an electrophoresis gel that uses an electrical field to separate the negatively charged molecules according to their size and weight. Finally, the fluorescent colors of the terminator bases are recorded by autoradiography. Each color corresponds to a specific base (A,C,G or T) which allows scientists to rebuild the DNA sequence. 

The HGP permitted important progress in several fields, beginning with the medical one. Indeed, even if the whole human genome sequence hasn’t been interpreted yet, it enabled scientists to better comprehend the operation of numerous diseases, involving genetic mutations such as cancers, and helped position the research towards gene therapy. Thus, huge studies such as the Pan-Cancer of Whole Genomes Analysis Project were launched, enabling scientists to identify common patterns of mutation in more than 2,600 cancer genomes. 

Furthermore, this breakthrough gave rise to a wide variety of discoveries in the genetic field. For example in 2011, Emmanuelle Charpentier and Jennifer Doudna developed a complex associating an RNA strand with a Cas9 enzyme. This enzyme is similar to the ones used by bacterias during viruses’ infections to cut the virus’s DNA and thus get rid of the intruder. Thanks to these “genetic scissors” also called crispr-cas9 and to the knowledge of the human’s genome, scientists are now able to edit the DNA in order to correct it with precision. This discovery thus leads to numerous potentialities, e.g. concerning the search of cures to genetic diseases.

Moreover, the HGP enabled scientists to rediscover from a different point of view the kinships existing between all living beings. The human genome redefines in particular our identity as a species and our place within other species in nature.  

Indeed, it enabled scientists to trace back in precision the evolution of the human species from the first Homo Sapiens, whose skull was found in Morocco, dating from more than 300 million years. It also allowed them to study the other Homo species that coexisted with Homo Sapiens, such as Neanderthals or Denisovans, and their exchanges with our species.

Besides, the study of the human genome led to many striking anthropological realizations. For example, it has appeared that humans are sharing 98% of their genes with the chimpanzees. These facts question our traditional perception of the animal world and the limits between the human species and other species.

It has also been observed that many genes from the human genome are coming from viruses’ genomes, that is to say from other species’ genomes, given the fact that viruses are only vectors of genes. Indeed, viruses, when infecting a host, tend to release their DNA in the host cell but also can absorb genes from the latter. These genes can then be re-transmitted to other organisms during an infection. This realization brings to light the fact that evolution happens not only in a vertical way, from generation to generation of the same species, but also in a horizontal way, between non-related individuals and sometimes from very different species; a fact that enriches even more the biodiversity. 

In addition to enlightening us on the history of our species evolution, DNA sequencing allows us to better comprehend our own history. Indeed, the business of DNA testing has become more and more popular these last few years. It is now possible and easy to get precise information about one’s origins, ancestors and pourcentages of affiliation to a specific region of the world. The cost of these tests has dropped since their invention and is largely under the actual cost of the scientific process that it requires. Indeed, a lot of the companies offering these prices are selling at a profit their clients’ genetic data to business partners such as big pharmaceutical industries or laboratories. This raises questions about the confidentiality of such valuable information. Should the DNA be a common property, thus allowing searchers to use it in order to advance in their research? But wouldn’t it be risking that this information could be used for bad purposes, e.g. allowing governments to keep precise records about their population? 

As a conclusion, the knowledge and techniques in the genetic field have known a swift progress these last few years and continue to be developed. Indeed, if the genome have been completely sequenced in 2003, a large part of it still remains indecipherable for scientists today. As it becomes more and more easy to manipulate and modify the genome thanks to high technology tools, questions are springing up and might be summarized in one: How far should we go? 

Logo of the Human Genome Project

Bibliography:

Whole-Genome Sequencing Methods

La révolution de la génomique : les nouvelles méthodes de séquençage et leurs applications

Le séquençage du génome

Genome Editing with CRISPR-Cas9

Sequencing Genomes – Genomes

How Sanger Sequencing Works? (Classic Sanger Method)

The Human Genome Project: A Player’s Perspective

Qu’est-ce que CRISPR, le « ciseau génétique » à ne pas mettre entre toutes les mains ?

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