 Advances in gene targeting technologies which hijack the homologous recombination mechanics of cells are now leading to the development of a new wave of more accurate , isogenic human disease models . These engineered human cell models are thought to more accurately reflect the genetics of human diseases than their mouse model predecessors . This is largely because mutations of interest are introduced into endogenous genes , just as they occur in the real patients , and because they are based on human genomes rather than rat genomes . Furthermore , certain technologies enable the knock @-@ in of a particular mutation rather than just knock @-@ outs associated with older gene targeting technologies . 
