Question

Question 51 Not yet answered Strain R of E. coli has an RM system that modifies/cleaves the sequence GAATTC. Sometimes invading phage DNA is methylated by the strain R methylase before the endonuclease can cleave the viral DNA, and then replicates in the methylated form and forms viral particles. If you add some of these viral particles to uninfected bacteria of strain R, what will happen? Points out of 2.50 P Flag question Select one: O a. The invading phage DNA is methylated and thus cleaved by the strain Rendonuclease O b. Strain R is resistant to all phage, no matter the source c. The invading phage DNA is unmethylated and will be cleaved by the strain Rendonuclease d. The invading phage DNA is unmethylated and is protected from the strain Rendonuclease O e. The invading phage DNA is methylated and protected from the strain Rendonuclease

Answer 1

The invading phage DNA is methylated and protected from strain R endonuclease.

In host 1 the Eco R1 target site in the phage genome got modified by methylation and then the methylated phage DNA is copied and many progeny viral particles are assembled in the host cell and they are released by the lysis of the host cell. When these phges infect a seond host they are immune to the RE (Eco RI) of host 2 because the phage DNA is methylated at the EcoRI target site. A methylated target site is not a substrate for restricton enzyme and therefore the resriction enzyme of the second host do not cleave the phage DNA. So the phage can successfully infect the second host.

All the statements regardng oxidative phosphorylation are true