Oxford - With the deciphering of the genome of 1,092 people from 14 different ethnic groups, the international 1000 genome project has achieved its goal. One of the results published in Nature (2012; doi: 10.1038 / nature11632) is that healthy people also have numerous genetic errors in their proteins.
Two years ago when the pilot study was presented it was already said: “No genome is perfect ". At that time, the gene sequence of 179 people had been deciphered, in further 697 people the protein-coding segments (exome) of the genetic material had been deciphered. The data are now available for all 1,092 participants. For the exome, the sequence of each participant was determined between 50 and 100 times. This high number is necessary to get to all parts of the genome.
For the sequencing, the genetic material namely be broken down into small snippets. Putting this puzzle back together later without gaps is only possible when sequencing with new pieces each time. The project itself indicates the limit to perfection with around 28 sequencing rounds. This effort was avoided for reasons of cost for the large mass of the genetic material that does not contain any information for proteins. Here, Gil McVean's team chose "low coverage" with 2 to 6 sequencing.
The more detailed exome analysis shows that even healthy people - the participants in the study were free from identifiable diseases - have genetic defects. On average, there were 120 to 400 mutations, 10 to 20 of which led to the formation of functionless protein and two to five mutations damaged the protein altogether. Another 1 to 2 mutations were found in genes that are associated with the development of cancer.
The fact that people with gene defects still remain healthy is attributed to the fact that the team led by Gil McVean from the University of Oxford says that most Genes (on the homologous chromosomes) are duplicated. Some of them have multiple copies on the individual chromosomes, so that single mutations often have no consequences. It is also conceivable that the mutation affects cell functions that are irrelevant for the individual. An example would be disruption of alcohol breakdown for people from cultures in which alcohol is frowned upon.
Knowledge of the “normal” gene frequency could influence medicine in two areas. On the one hand, it becomes easier to find the genetic defects responsible for hereditary diseases. On the other hand, according to Gil McVean, the genome-wide association studies will benefit. These look for gene variants that are responsible for the familial accumulation of many diseases. These studies could benefit from the fact that the reference database is becoming more and more precise.
The project is now to be expanded to include data from further 1,500 genomes from twelve previously unrecorded population groups. So far, people from 14 different ethnic groups from all continents have taken part. These included Africans from Nigeria and Kenya, Han Chinese from Beijing and southern China, Japanese from Tokyo, Whites and Afro-Americans and those of Mexican or Puerto Rican origin, Italians, British, Finns, Spaniards and Colombians, but not Germans.
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