The reactivation of developmentally inert 5S genes in somatic nuclei injected into Xenopus oocytes

Abstract
In Xenopus borealis and X. laevis, the somatic-type 5S rRNA genes are active in all cells; the oocyte-type 5S genes are active in oocytes but not in somatic cells. A new method of native gel electrophoresis resolves the 2 types of 5S RNA, which are of the same length but different sequence both interspecifically and intraspecifically. When somatic nuclei were injected into oocytes, their inactive oocyte-type 5S genes often remained inactive, and has thus conserved their developmentally regulated condition. Other conditions, which include treatment with 0.35 M NaCl, reactivated the genes.