MACRONUCLEAR GENE-SIZED MOLECULES OF HYPOTRICHS

The macronuclear genome of hypotrichous ciliates consists of DNA molec ules of gene-sized length. A macronuclear DNA molecule contains a sing le coding region, We have analyzed the many hypotrich macronuclear DNA sequences sequenced by us and others. No highly conserved promoter se quences nor replication initiation sequences have been identified in t he 5' nor in the 3' non-translated regions, suggesting that promoter f unction in hypotrichs may differ from other eukaryotes. The macronucle ar genes are intron-poor; similar to 19% of the genes sequenced to dat e have one to three introns. Not all macronuclear DNA molecules may be transcribed; some macronuclear molecules may hot have any coding func tion. Codon bias in hypotrichs is different in many respects from othe r ciliates and from other eukaryotes.