Repeat-Induced Transcriptional Repression is Time Dependent. (a) Primer extension products are shown from mRNA pools taken from oocytes injected with 5 ng of pHSVtk-CAT (no repeats), or pHSVtk-CAT (CGG70) and with 0.3 ng pCMV-CAT as a control for the transcriptional competence of the oocytes. Lane numbers refer to time in hours post-injection. CON represents no oocyte injection and CAT refers to an injection of 0.3 ng pCMV-CAT alone. Primer extension products corresponding to, CMV-CAT and HSVtk-CAT mRNAs are shown. (b) A graphical representation of levels of transcription from the HSV-TK promoter based upon data shown in panel A. Transcription levels are normalised to the co-injected pCMV-CAT control and for background signal. (c) A Southern blot of a chloroquine supercoiling assay of injected pHSVtk-CAT (CGG)70 DNA. Time points of injection mirror those of panel (b). Lane I represents input DNA, other lane numbers refer to time in hours post-injection.