Defective interfering particle

In virology, defective interfering particles (DIPs), also known as defective interfering viruses, are spontaneously generated virus mutants in which a critical portion of the particle's genome has been lost due to defective replication. DIPs are derived from and associated with their parent virus, and particles are classed as DIPs if they are rendered non-infectious due to at least one essential gene of the virus being lost or severely damaged as a result of the defection. A DIP can usually still penetrate host cells, but requires another fully functional virus particle (the 'helper' virus) to co-infect a cell with it, in order to provide the lost factors. The existence of DIPs has been known about for decades, and they can occur within nearly every class of both DNA and RNA viruses.