Santa's Little Helper Santa's Little Helper Santa's Little Helper is a recurring character in the American animated television series "The Simpsons". He is the pet greyhound of the Simpson family. The dog was introduced in the first episode of the show, the 1989 Christmas special "Simpsons Roasting on an Open Fire", in which his owner abandons him for finishing last in a greyhound race. Homer Simpson and his son Bart, who are at the race track in hope of winning some money for Christmas presents, see this and decide to adopt the dog. Santa's Little Helper has since appeared frequently on "The Simpsons",
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