Isolation andFunctional Analysis ofSporulation-Indu ced Transcribed Sequences fromSaccharomyces cerevisiae

sporulation-induced transcripts wereisolated fromagene-size insert yeast-X recombinant DNA library, bydifferential-pla que filter hybridization. Anattempt wasmadetodetermine thefunction ofthree ofthese genes bymutating theminthe yeast genomewithinvitro mutagenesis andone-step genereplacement techniques. Onegenewasextensively disrupted bybotha0.3-kilobase deletion andtheinsertion oftwolarge DNA sequences atdifferent sites within thegene. Surprisingly, this compound mutation didnotappear toaffect meiosis ortheproduction ofviable ascospores, indicating that this genewasdispensable fordifferentiation. Theother twogenes weredisrupted by simple insertion mutations atasite whereitwaspossible that theymight still possess somegeneactivity. These mutations also didnotappear toaffect sporulation. Theseresults suggest thatnotallsporulation-induced genes