complementation
1. The ability of one chain of polynucleotides (either DNA or RNA) to form hydrogen bonds with another chain because of a coincidence of adenine/thymine pairs of bases and guanine/cytosine pairs of bases on each strand. 2. Genetic complementation is the ability of one mutant to supply a required function to another mutant. See cis-trans test. 3. Also, cloning by complementation is a technique in which a mutant host cell (e.g., lacks the ability to synthesize some nutrient) is infected with a library and a clone is picked that has the ability to synthesize the nutrient. This clone is derived from a mutant cell that picked up a recombinant molecule containing a functional gene that has the ability to replace its own faulty one.