Abnormal RNA synthesis in sex vesicles of tertiary trisomic male mice

The XY bivalent contained within the sex vesicle of chromosomally normal male mice shows virtually no RNA transcriptional activity as measured by autoradiography during the prophase of meiosis. Tertiary trisomic males, derived from the T 70 H and T 31 H reciprocal translocations, include the extra small marker chromosome to varying degrees within the sex vesicle. It has been found that RNA transcription occurs within the sex vesicles of such trisomics. An attempt has been made to correlate such activity either to the extra marker chromosome itself or to a possible reactivation of the normally quiescent sex bivalent. The relationship of the abnormal RNA synthesis to the breakdown of meiosis in tertiary trisomics and to their subsequent reduced fertility is discussed.