Parajumpers Parka,Parajumpers Gobi LeatherIt has not been possible to view the transcriptional activity of a single gene within a living eukaryotic cell. It is therefore unclear how long and how frequently a gene is actively transcribed, how this is modulated during differentiation, and how transcriptional events are dynamically coordinated in cell populations. By means of an in vivo RNA detection technique , we have directly visualized transcription of an endogenous developmental gene. We found discrete "pulses" of gene activity that turn on and off at irregular intervals. Surprisingly, the length and height of these pulses were consistent throughout development. However, there was strong developmental variation in the proportion of cells recruited to the expressing Parajumpers Parka pool. Cells were more likely to re-express Parajumpers Gobi Leather than to initiate new expression, indicating that we directly observe a transcriptional memory. In addition, we used a clustering algorithm to reveal synchronous transcription initiation in neighboring cells. This study represents the first direct visualization of transcriptional pulsing in eukaryotes. Discontinuity of transcription may allow greater flexibility in the gene-expression decisions of a cell.Comment inEukaryotic transcription: what does it mean for a gene to be 'on'? [Curr Biol. 2006]Eukaryotic transcription: what does it mean for a gene to be 'on'?Golding I, Cox EC. Curr Biol. 2006 May 23; 16(10):R371-3.