**Abstract**

Now there is interest in finding factors that, once in the ovum, can affect the development of offspring. The *sbr* (*Dm nxf1*) gene in *D. melanogaster* belongs to the evolutionarily conserved family of nxf (nuclear export factor). It is involved in controlling of male fertility and forming the factor that affects the segregation of maternal and paternal chromosomes after fertilization. The Dm NXF1 (SBR) protein seems to play a role in forming this mysterious factor during the meiotic period of spermatogenesis. Male germ cells develop as a syncytium, and success of spermatid individualization depends, to a great degree, on gene expression in primary spermatocytes. Most transcripts formed in primary spermatocytes are long-lived. The presence of the Dm NXF1 protein in the nucleus as well as in the cytoplasm suggests that it plays a role in the biogenesis of long-lived RNA and in cytoskeletal reorganization.

**Keywords:** spermatogenesis, meiosis, *Drosophila*, NXF, cytokinesis, RNA-binding protein
