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The human genome is 99% decoded, the American geneticist Craig Venter announced two decades ago. What has the deciphering brought us since then?
The decoding of the genome was a sensation, although the announcement by Craig Venter on April 6, 2000, was somewhat premature. It actually took another year before the Human Genome Project (HGP), which was in competition with Venter, published its peer-reviewed research results in the scientific journal Science and Nature on February 15, 2001.
Battle for first place
The decoding of the genome was a race for scientific fame — between the HGP, which is government-funded by the US, and Venter with his private company Celera Genomics. The government researchers lagged somewhat behind Celera Genomics in their work. By April 2000, they had been able to decode only 54% of the human genome.
The genome is made up of the genetic storage material deoxyribonucleic acid (DNA). It contains all hereditary information of life.
Craig Venter 1998 in the laboratory of his company Celera Genomics. Venter invented the shotgun sequencing method.
Going after the genetic material with a shotgun
Venter used a different sequencing method than the HGP researchers: namely, the so-called shotgun method that he developed. In this method, the individual DNA fragments are generated randomly. This is similar to shooting at the long chain with a shotgun and then looking at and reading out the fragments individually.
However, Venter also used HGP data to achieve his goal. And that was an ambitious one: The human genome consists of 3.2 billion base pairs — the letters of life, so to speak. Finding them all was a mammoth task for him and the competing researchers. But the design of this genetic chain is actually quite simple.
It consists of a sequence of only four different building blocks: the DNA bases cytosine (C), guanine (G), adenine (A) and thymine (T). It is the sequence of these bases that determines our eye or hair color or whether we have any hereditary diseases.
Read more: Stone-Age 'chewing gum' reveals human DNA
Many doors leading nowhere
Only a few sections of the entire genome are the genes that contain important instructions for building blocks of life such as proteins. "According to current knowledge, however, a large proportion of DNA is an evolutionary remnant and has no function whatsoever. This makes it clear that although the door to the code of life has been opened, countless new doors are hidden behind it," writes chemist Friederike Fehr from the Max Planck Institute for Dynamics and Self-Organization in Göttingen.
Many genes that were discovered in the genome sequence had been unknown until then. "So the effects or tasks associated with them must also be researched. The sequence of letters alone is of limited help in this regard," Fehr writes.
Long road to medical applications
It was only with the completion of sequencing that the project of decoding the human genome could bear practical fruit. Although Venter published his own personal genome in the scientific journal PLoS Biology in 2007, this, too, was of rather symbolic importance. Gene sequencing in itself was only a first step toward a fundamental change in our medicine.
Scientists still had to research and assign the respective functions of the individual building blocks of the genome, i.e. find out which building block is responsible for what. They did this with the help of mice. Their genome is largely identical to that of humans and thus provided a basis for understanding the functions of human genes.
Experts believe that it could take dozens, if not hundreds, of years to really understand the human genome.
What do we get out of this?
The genomes of two people differ. These differences are the basis for the genetic predisposition to certain diseases.
Increasingly, genetic tests are being offered that enable experts to identify some of these predispositions and thus determine whether or not a person carries an increased risk of disease. A saliva sample is sufficient for this.
The most important thing in all these tests is to interpret the results correctly, for example, to determine if there is the disposition for Alzheimer's or diabetes.
With the help of genome research, it is now possible to identify various gene functions. This in turn helps doctors to treat certain diseases, including in children with an immune deficiency that is hereditary. Doctors can even implant new genes into these children to treat the disease.
Breast and ovarian cancer become apparent in the alterations of two genes (BRCA1 and BRCA2). A genetic risk for a tumor disease can be detected only in a few cases by genetic analysis.
There is still much to be done
The human genome consists of roughly 22,500 genes. Researchers around the world were astonished at this result as, believe it or not, a water flea has 30,907.
How complex a living being is, therefore, not dependent only on the number of genes. US President Bill Clinton said on April 6, 2000: "Now we are learning the language with which God created life." We now know that we still need a lot more vocabulary before we master that language.
This article has been edited and corrected since it's first publication on 5 April 2020