Before revision:  In particular, we derive exact expressions for the first two moments of the distribution of nascent RNA molecules for an arbitrary mechanism of transcription initiation. These theoretical results are applied to published data on the nascent RNA distributions obtained for a collection of constitutively expressed yeast genes.
After revision:  In particular, we derive exact expressions for the first two moments of the distribution of nascent RNA molecules and apply our theory to published data on the nascent RNA distributions obtained for a collection of constitutively expressed yeast genes.