Two hundred years of vaccination

proposed that could activate transcription of numerous genes in spermatids. If a gene is transcribed and its protein accumulates in spermatids, it is very possible that the protein will function there. Regulation of holoenzyme levels might also contribute to other cases of cell-type-specific gene regulation. Although no other cells seem to accumulate as much of the basal transcription machinery as early spermatids do, overall transcription rates do vary by more than an order of magnitude between different somatic tissue types [9]. Thus, differences in levels of the basal transcription machinery may be of wide-spread importance in determining patterns of cell-type-specific gene expression.