The vast majority of genetic disorders (schizophrenia or breast cancer, for example) have different effects in different people. Moreover, an individual carrying certain mutations can develop a disease, whereas another one with the same mutations may not. This holds true even when comparing two identical twins who have identical genomes. But why does the same mutation have different effects in different individuals?
Since the early twentieth century researchers have studied the role that genetic variability (mutations) and the environment (consumption habits, lifestyle, etc.) have in the development of diseases. “However, genetic and environmental differences are not enough” said Alejandro Burga, one of the authors of the article. “In the last decade we have learned by studying very simple organisms such as bacteria that gene expression — the extent to which a gene is turned on or off — varies greatly among individuals, even in the absence of genetic and environmental variation. Two cells are not completely identical and sometimes these differences have their origin in random or stochastic processes. The results of our study show that this type of variation can be an important influence the phenotype of animals, and that its measurement can help to reliably predict the chance of developing an abnormal phenotype such as a disease .”