Santa's Little Helper the show in minor appearances, although there have been some episodes that feature him heavily, including the first episode of "The Simpsons". In that episode, "Simpsons Roasting on an Open Fire" (season one, 1989), Homer discovers that he has no money to buy Christmas presents for the family. Desperate for a miracle, he and Bart go to the greyhound racing track on Christmas Eve in hopes of winning some money. Although Homer has inside information on which dog is the most likely to win, he instead bets on a last-minute entry, Santa's Little Helper (here despite being brown), believing the
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