Santa's Little Helper the show, but voice artist Frank Welker has also voiced him. Santa's Little Helper has become a popular character following his appearances on "The Simpsons". He ranked 27th in Animal Planet's 2003 television special "50 Greatest TV Animals" that was based on popularity, name recognition, and the longevity of the shows. He has also been featured in merchandise relating to "The Simpsons", such as video games, board games, and comics. Santa's Little Helper is a greyhound that appears on the animated television series "The Simpsons" and is the pet dog of the Simpson family. He can often be seen on
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