Say you are studying a disease in human patients, such as diabetes and obesity, and you are looking at the human DNA sequence to try and find out whether specific mutations could be contributing to it. As all mammals shared a common ancestor approximately 80 million years ago, their genomes show great similarities. This means that non-human mammals can be used as experimental models for human disease. So, to narrow down the number of suspects (disease causing mutations), you might want to compare the human genome with that of a well-established experimental model – such as the mouse – showing the same condition (phenotype): if these mice have the same mutations, this would provide an indication that the genes in question have the same function in both organisms. You have now found mouse models you can use to study the human disease, or you may look deeper into the pathways behind glucose metabolism in which these genes are involved.  Read more