Question

Prediction the phenotype of lambda phage-infected bacteria conferred by the mutations described in the following. Explain your reasoning.

a. A mutation creating a protease-resistant λ CII protein.

b. A mutation of λ O_R2 that will prevent protein binding.

c. A mutation that inactivates the λ N gene.

d. A mutation in the gene encoding the λ CI protein.

Answer 1

Answer
cIl:The protein help in transcription of cl and integrase .Integrase insert the phage genome into the host genome.At low integrase concentration there is no effect but at its high concentration along with xis low concentration it will integrate the genome.if integrase and xis is low it disrupts from host genome.

OR2: It binds to the cl and also bound to OLR2 and dimerise the cl to and help in dicreasing it’s concentration leads to lytic cycle.

N: It is RNApol antitermination protein it binds to the normal rna polymerase and it missed to terminate the synthesis of later lambda phase gene help in infection.

Cl: cI protein is directly in relation with transcription of cro genes.In its low concentration transcription of cro genes takes place which is helpful in converting the lysogeny cycle into lytic cycle.

So,
B : In b mutation of λ OR2 that will prevent protein binding of OR3 to OL3R which leads to increase the cl concentration and maintain lysogeny.