In the 1940's, Avery, MacCleod, and McCarty transformed nonencapsulated bacteria into encapsulated forms by growing the nonencapsulated cells in a culture containing an extract made from dead encapsulated cells. The transformed cells produced colonies of encapsulated bacteria. Three different procedures and their results are outlined below.
Procedure I
Exact made from dead encapsulated cells added to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Both nonencapsulated and encapsulated bacteria grow.
Procedure II
Extract made from dead encapsulated cells treated with protein-degrading enzymes
before adding exact to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Both nonencapsulated and encapsulated bacteria grow.
Procedure III
Extract made from dead encapsulated cells treated with DNAse (an enzyme that
selectively destroys DNA) before adding extract to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Only nonencapsulated bacteria grow.
(A) To demonstrate that the transforming factor is an enzyme
(B) To demonstrate that the transforming factor is not a protein
(C) To destroy nucleic acids in the exact
(D) To destroy any capsules in the exact
(E) To prevent the extract from being contaminated by nonencapsulated bacteria
Answer: B
Procedure I
Exact made from dead encapsulated cells added to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Both nonencapsulated and encapsulated bacteria grow.
Procedure II
Extract made from dead encapsulated cells treated with protein-degrading enzymes
before adding exact to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Both nonencapsulated and encapsulated bacteria grow.
Procedure III
Extract made from dead encapsulated cells treated with DNAse (an enzyme that
selectively destroys DNA) before adding extract to culture medium.
Nonencapsulated bacteria added to culture medium.
Results Only nonencapsulated bacteria grow.
What was the purpose of treating the extract with protein-degrading enzymes in Procedure II
(A) To demonstrate that the transforming factor is an enzyme
(B) To demonstrate that the transforming factor is not a protein
(C) To destroy nucleic acids in the exact
(D) To destroy any capsules in the exact
(E) To prevent the extract from being contaminated by nonencapsulated bacteria
Answer: B