Traditional analysis of mutants (natural or induced) to determine gene function is known as

The given blank can be filled with forward genetics.  

Forward genetic screen or forward genetics refers to a method used to determine a set of genes or genes accountable for a specific phenotype of a species. On the other hand, reverse genetics or reverse genetic screen evaluates the phenotype of a species following the disruption of a known gene.  

The method of forward genetics was initially done by inducing mutants with radiation, by using naturally occurring mutations, insertional mutagenesis, or chemicals.  

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.