Guidelines for checkpoints
Gene products should not be annotated to checkpoint terms based on mutations that result in activation of the checkpoint (i.e, cause cell cycle arrest). Such mutations cause a problem which is detected by the checkpoint sensor, and cell cycle arrest indicates that the checkpoint is functioning normally. This does not represent positive regulation of the checkpoint since the mutated gene is not necessarily part of the checkpoint in a normal cell. Gene products can be annotated to checkpoint terms when a mutation results in inactivation of the checkpoint. This includes, recruiting the checkpoint signalling components, part of the sensor machinery detecting the damage, or any component of the signalling pathway to the effector. Genes which are involved in correcting the problems detected by the checkpoint should also not be annotated to the checkpoint terms, because they act downstream of the checkpoint. These genes should instead be annotated to "response to checkpoint x" terms, which are in a separate branch of the ontology.