Meiotic induction of EXO1 transcription. Total RNA from a wild-type diploid (HTY525) was isolated at the indicated times during meiosis, fractionated on formaldehyde agarose gels (0.7%), and subjected to Northern blot analysis. (A) Transcription of the EXO1 and ACT1 genes was monitored with EXO1 (0.9-kb EcoRI fragment from pHT130) and ACT1 (0.6-kb ClaI fragment from pYA301) coding sequences as probes. The ACT1 transcript, which is expressed at a constant level during meiosis, was used as an internal control (McKee and Kleckner, 1997). (B) Relative intensity of the EXO1 transcript compared with that of ACT1. At each time, the intensities of the EXO1 and ACT1 bands were measured and the amount of EXO1 transcript was divided by the amount of ACT1 transcript.