Mutations to essential genes are generally lethal and hence temperature-sensitive mutants enable researchers to induce the phenotype at the restrictive temperatures and study the effects.
[4] In the 1970s, several temperature-sensitive mutant genes were identified in Drosophila melanogaster, such as shibirets, which led to the first genetic dissection of synaptic function.
However, a co-infection under restrictive conditions with two ts mutants defective in different genes generally leads to robust growth because of intergenic complementation.
Intragenic complementation of ts mutants defective in the same gene can provide information on the structural organization of the multimer.
[8] Growth of phage ts mutants under partially restrictive conditions has been used to identify the functions of genes.
[11][12] For example, growing a ts DNA repair mutant at an intermediate temperature will allow some progeny phage to be produced.