The word “factor” is often seen used in manuscripts of molecular biology and biochemistry as a fancy way of saying unknown. Before the inner workings of complex genetic of molecular pathways are understood, there are often clues that suggest the presence and operation of certain unknown and unnamed components which might be labeled factor for lack of a better term (e.g. transcription factor, or translation initiation factor). Later these factors may become well described; sometimes the term factor is dropped or in some cases, especially where it was applied to a single instance of what is a large family of More >