Synthesis of late transcripts begin at 16.45 map units and extend to 99 map units. Extensive splicing of this large transcript then occurs. In general their are 5 classes of late transcripts which have variable 5'ends and coterminal 3' ends. They do not encode polypeptides and have the potential to form extensive secondary structure. The synthesis of late proteins is maximal 20 hr post-infection.
Most late proteins are structural components of the virion but some early genes are also made late.