Stop! Or My Dog Will Shoot Wiggum, enroll him in the Springfield Animal Police Academy, where he is teamed with Lou, managing to help fight crime in Springfield. Santa's Little Helper catches Snake Jailbird who is taken to court, but freed on a technicality. This makes Santa's Little Helper jaded, and when he returns home, he bites Bart on the leg out of frustration. Considering the fact that the pressure from the fight against crime is what led to the dog's actions on Bart, the Simpsons send the dog away to live with Lou. As a replacement, Marge buys Bart a reticulated python, which he names
Helper dependent virus and capsid encoding DNA, plus helper DNA. Every cell that is successfully transfected with all three DNA fragments will produce the necessary proteins to produce infective viruses. These viruses will only have transgenic DNA encapsidated and therefore once they've infected a patient's cell, they will not be capable of reproducing. Helper dependent viruses can also occur in nature without being "gutted". The term satellite virus has been given to a large group of viruses that all require the presence of another virus to replicate. Many of these are plant viruses, but animal viruses can be seen in the case of