Question

The gene for a restriction enzyme from one bacterial species (donor) is put into a totally different bacterial species (the recipient) and its protein is made (the restriction enzyme), but all of the recipient bacteria quickly die. What is the most likely reason for this?

the restriction enzyme binds the recipient's peptidoglycan and blocks cell division

the restriction enzyme from the donor binds the recipient's DNA and cuts it up since the recipient doesn't have that particurlar modification system

the restriction enzyme binds the recipient's DNA and blocks replication

the restriction enzyme binds the recipient's mRNA and inhibits translation

Answer 1

Correct option: The restriction enzyme from the donor binds the recipient's DNA and cuts it up since the recipient doesn't have that particular modification system.

Explanation: Restriction enzymes were evolved in bacterial systems to cut (at specific sites) and destroy any foreign DNA, particularly from viruses. The bacterium producing the protein restriction enzyme also evolve mechanisms to prevent being cut by its own restriction enzyme. Most often these prevention mechanisms rely on methylation on specific DNA sites (maybe exactly in the cut site). Hence, one bacteria expressing another bacteria's restriction endonuclease is not protected by this prevention mechanism ( one bacteria only modify at sites it know could be cut by its own endonuclease). Consequently, bacteria expressing foreign restriction endonuclease succumb to the enzyme.