Chromatin Structure and Transcription

Abstract

Transcription of eukaryotic genes appears to proceed in a quite different manner and to obey very different rules than the corresponding process in prokaryotes. In a typical prokaryotic organism, the genome is small, and much of it is transcribed. Polycistronic messages are common, but intervening sequences are not. A single RNA polymerase is used for all genes. In eukaryotes, much of this has been changed. In a typical differentiated cell of a higher organism, the genome is immense, and only a small fraction (~5 to 10%; Davidson, 1976) is transcribed. Polycistronic messages are rare, but intervening sequences are common, and many of the transcripts must be spliced to produce messages. Three different RNA polymerases are employed, each specific for certain kinds of genes.