Model systems Transgenic mice construction germline modification login to view 5 more bullets the altered phenotype with the added gene is observed through the entire lifespan login to view 1 more bullet number of gene copies is variable altered phenotype passed to offspring as it is a germline mutation function studying dominant disorders login to view 1 more bullet Knockout mice construction similar to transgenic mice except instead of adding a foreign gene, a normal gene is removed also a germline modification function useful for studying loss-of-function mutations in human diseases Chimeric mice construction a genetic mix between two distinct cell lines fusion of two early embryogenic lines in embryogenesis two lines recognized as self due to absence of immune system function can reproduce to create offspring of various types in subsequent generations login to view 3 more bullets Cre-lox system construction a system that allows turning on/off of gene of interest with an antibiotic-controlled promoter function to study a gene whose deletion is lethal to embryos login to view 1 more bullet can also study the timing of when a gene is important in development RNAi construction dsRNA is synthesized complementary to the mRNA sequence of interest transfected into cells dsRNA separates and binds the complementary mRNA dsRNA (where one strand is the host mRNA) is seen as a viral product and degraded function ↓ expression of a particular gene