Years ago, the Kahn lab pioneered techniques to genetically modify given cell types to «knock out» the insulin receptor protein on the cell surface, which activates insulin's actions in the cell, thus creating a state of insulin resistance just in these cells. (joslin.org)
While all cells in a specific organism share the identical DNA sequence, only a fraction of those genes are activated in a given cell type. (sciencedaily.com)
However, in any given cell type, only a fraction of this information is actually used. (sciencedaily.com)