Question

Avery, MacLeod, and McCarty (1944) demonstrated that DNA was the genetic material by treating heat-killed Streptococcus pneumoniae S (smooth) strain with DNase, thereby preventing transfer of the "transforming substance" from the killed S strain to the live R (rough) strain when the two were mixed together and injected into mice. Another way that one could demonstrate transformation in bacteria would be to extract DNA from

A) an R strain and mix it with cells of an S strain.
B) both S and R strains and mix it to allow recombination to take place.
C) an ampicillin-sensitive strain and mix it with cells of an ampicillin-resistant strain.
D) an S strain and mix it with cells of an R strain.
E) None of the above are correct.

Answer 1

The correct approach to demonstrate transformation in bacteria after Avery's experiment is to introduce DNA from an S strain to an R strain; options A, B, and C would not demonstrate transformation respectively. Option D is the correct answer.

Step-by-step explanation:

The experiment proposed by Avery, MacLeod, and McCarty in 1944 strongly indicated that DNA was the substance responsible for genetic transformation in bacteria.

If another demonstration of transformation is needed, the correct approach would be to extract DNA from one strain and introduce it to another strain to observe a transformation. Considering the options provided, the correct answer is D) an S strain and mix it with cells of an R strain.

This is because the DNA from the S strain, which carries the genetic information for smooth capsules and pathogenicity, could potentially transform the non-pathogenic R strain cells into a pathogenic form when mixed, which would then be a direct demonstration of DNA as the transforming factor.