Restriction enzymes were first discovered with the observation that?

Question

a. DNA is restricted to the nucleus

b. phage DNA is destroyed in a host cell

c. foreign DNA is kept out of a cell

d. foreign DNA is restricted to the cytoplasm

e. all of the above

Answer 1

a.

Answer 2

Answer = b.

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Restriction enzymes were first discovered in the 1950s when evidence for a sort of primitive immune system was found to exist in bacteria. It was observed that certain strains of E. coli

were resistant to infection by various bacteriophages. This phenomenon seemed to be a property of the bacterial cell itself, an ability to restrict the growth and replication of the attacking phages. In 1962, at the University of Geneva, it was found that the resistant bacterium possessed an enzyme system that selectively recognized and destroyed foreign phage DNA within the bacterial membrane and at the same time modified the chromosomal DNA of the bacterium

to prevent self-destruction.