Simpsons Roasting on an Open Fire to waste money on getting his son Bart's tattoo removed. He decides to keep their financial troubles a secret and gets a job as a shopping mall Santa Claus, but later discovers that the job does not pay enough. Desperate for a miracle, Homer and Bart go to the dog-racing track on Christmas Eve in hopes of earning some money but end up adopting an abandoned greyhound, Santa's Little Helper. The episode was written by Mimi Pond, and it was directed by David Silverman. "Simpsons Roasting on an Open Fire" was nominated for two Emmy Awards in 1990, and has
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