L

R

R

As soon as the phage infects the bacterial cell, its genome gets circularized. The transcription begins at the two promoters Pand Psituated at the left and the right respectively. The first gene taken for the transcription process is known as the cro gene. It is present near the Ppromoter. This gene synthesizes a product known as cro protein. It helps the phage in switching over to the lytic cycle. The first gene from the right side taken for the transcription is known as the N gene. This gene encodes a protein known as N protein. It is a transcription anti-terminator. The result of N protein includes the transcription of genes such as cII, O, P, and Q genes respectively. A gene known as cI gene encodes the lambda repressor. This gene gets turned on through cII gene product. The int gene also gets switched on due to the activity of cII protein. This gene encodes for the integrase enzyme. It helps in integrating the lambda chromosome into the host chromosome. The process of integration occurs during the lysogenic pathway. However, the cII protein gets activated only when the phage switches over to the lysogenic pathway. The genes O and P encode two DNA replication proteins. The gene Q encodes proteins required for activating the genes involved in lysis and production of phage proteins. The Q protein also acts as an anti-terminator. It permits the transcription of late genes.