Generation of transgenic mice. To express a transgene in vivo, the investigator first makes a construct containing the transgene being evaluated. A typical construct is illustrated in a. It contains a promoter that targets the transgene to the desired organ, the transgene being expressed, and intronic and polyadenylation sequences that ensure the proper processing of the mRNA transcripts that are produced. The methodology for generating transgenic mice is illustrated in b. Fertilized eggs are washed out of the oviducts of female mice. They are then microinjected under direct visualization and implanted into the uterus of pseudopregnant female mice. The genotype of the pups that are produced is evaluated in tail biopsy–derived DNA using PCR reactions or Southern blot evaluations.