"If poly A is added to poly U, to form a double or triple helix, the combination is inactive"

This quote by Francis Crick is referring to the process of forming a double or triple helix structure with two various types of polymers, poly A and poly U. When these 2 polymers are combined, the resulting structure is non-active. This implies that the mix of the 2 polymers does not have any biological activity. This is since the two polymers do not form a stable structure when integrated, and therefore can not carry out any biological functions. This is an important principle in molecular biology, as it assists to describe why certain combinations of particles are not able to form active structures. By understanding this idea, scientists can better understand how to develop active structures from various combinations of particles.