A new analysis of the human genome provides information on normal genetic variability between individuals and disease risk.
For the first time, the “average” human genome was characterized: that is, the range of genetic variability possible in human individuals was described, a useful result for understanding the contribution of genetic predisposition to diseases.
The study was conducted by scientists from the University of Exeter (United Kingdom) thanks to the analysis of two important genetic databases (the UK Biobank and the US All of US study) of which approximately 900,000 sequences were considered, and published in the scientific journal Genome Medicine.
Beautiful because it is varied
The “average” genome contains about 5 million variants, changes in the DNA sequence that makes up a gene. About 10,000 of these changes in position that differ between individuals alter gene sequences with possible positive or negative effects (such as different response to drugs, or lactose intolerance), but often offer neither benefits nor harm – therefore they have not been selected by natural selection and are not there for a reason, but for pure chance.
Furthermore, each of us has approximately one to three rare variants previously linked to serious genetic diseases and approximately fifty variants of uncertain clinical relevance. Speaking of diseases, when scientists analyzed the polygenic risk score, that is, the set of many small variations in DNA which, added together, can tell whether a person is more likely to develop a certain disease in the future, they realized that the majority of people would be considered at high genetic risk for around 3 of 28 common pathologies (for example diabetes, cardiovascular disease or schizophrenia).
Genetics is only part of the picture
“Importantly, we have discovered that each of us has a small number of genetic variants linked to certain diseases, although many of these do not actually cause any pathology in the individual,” explains Caroline Wright, Professor of Genomic Medicine at the University of Exeter and first author of the study. “It is therefore critical to consider context when interpreting genetic test results, taking into account symptoms, family history and other clinical and environmental risk factors.”
«Most people are not aware of how much genetic variability is present in each genome. In reality, variability is the norm. For the first time, our study outlines what to expect from the average human genome, which can help doctors and patients around the world understand, interpret and contextualize genomic data.”
