Class I genes are transcribed by the host cell's RNA polymerase before the viral genome completely exits the capsid.

Class II genes are then transcribed by T7 RNA polymerase and the host genome is degraded.

[1] According to ICTV's second report in 1976, the genus T7likevirus was first accepted under the name T7 phage group, unassigned to an order, family, or sub-family.

In 1998, the whole family was moved into the newly created order Caudovirales, and the genus was renamed again in the seventh report in 1999 to T7-like viruses.

[2] The genus was later renamed to Teseptimavirus under the newly established family Autographiviridae and subfamily Studiervirinae.