Extra-Chromosomal DNA in Early Stages of Oogenesis in Acheta Domesticus

Abstract

A large extra-chromosomal DNA body is found in gonial and oocyte nuclei of Acheta domesticus. Somatic cells within the ovary do not contain the DNA body which is limited to the nuclei of gametogenic cells. During early prophase of meiosis this body is spherically shaped and intensely Feulgen positive. Electron microscopy shows it to be composed of tightly packed fibrogranular material. The body is formed in the nuclei of premeiotic interphase cells where it first appears and a mass of dense chromatin material located within the nucleolus. In nuclei of early prophase cells the body is closely associated with the nuclear membrane. It increases in size, reaching a maximum in mid-pachytene nuclei. During late pachytene-early diplotene stage of meiosis the tight fibrillar material within the body loosens and takes on a less compact appearance. At the same time large fascicles of RNA-containing material accumulate within and around the DNA body. The amount of RNA material surrounding the body increases as the oocytes proceed into an arrested diplotene stage of development.