Question

In the late stages of infection of a bacterial cell by the bacteriophage T4, transcription of cellular genes stops because the bacterial core RNA polymerases are redirected to a set of "late" genes in the T4 genome, which are then transcribed at a high level. This transition depends on production of the bacteriophage proteins gp33 and gp55, which are similar to bacterial sigma proteins. What feature or property of the T4 late genes could enable this transition?

A. a different genetic code.

B. a shared sequence upstream from their transcription start sites.

C. a shared sequence downstream from their transcription start sites

D. translation by a different set of ribosomes.

E. a different start codon

Answer 1

B) A shared sequence upstream from their transcription start sites.

The proteins that are produced gp33 and gp55 protein which acts similar to sia factor makes this transition possible by binding on the promoter sequence upstream of the start site. This helps to recruit RNA polymerase to the promoter site of the late genes. Since RNA polymerase has more affinity to these proteins, transcription of these genes happen at a higher level than that of the cellular genes.