Abstract
The site of chromosomal DNA synthesis during zygotene stage of meiosis was explored by electron microscope autoradiography. Zygonema of Lilium longiflorum cultured in the presence of 3H-thymidine for 24 h frequently showed label distribution over the axial cores prior to formation of synaptinemal complexes. When the culture was continued in isotope-free medium, the zygotene label appeared over synaptinemal complexes. Light microscope autoradiographs of cells showed the zygotene label over both paired and unpaired regions of chromosomes at pachytene. The relevance of these observations to the formation of synaptinemal complex was discussed.
