Answer :
The crucial experiment being referred to likely involves the identification of DNA as the genetic material, famously demonstrated by the Avery-MacLeod-McCarty experiment in 1944.
In this experiment, the researchers were studying the transformation of non-virulent bacteria into virulent bacteria using material extracted from virulent strains. They used two strains of Streptococcus pneumoniae: a virulent, smooth strain (S) and a non-virulent, rough strain (R).
The key steps included:
Preparation of Extracts: Non-living (heat-killed) smooth (S) strain bacteria were used to extract the genetic material.
Enzymatic Treatment: This extracted material was treated with various enzymes to determine which component was responsible for the transformation of the living rough (R) strain into a virulent form.
Role of Deoxyribonuclease (DNase): Deoxyribonuclease, or DNase, is an enzyme that degrades DNA. When the bacterial extract was treated with DNase, the ability to transform the R strain into the S strain was lost.
Therefore, the bacterial strain whose genetic material is treated with Deoxyribonuclease enzyme is:
C) Non-living strain (S) before mixing it with the living strain (R).
This result showed that DNA was the transforming principle, as only the treatment with DNase, which degrades DNA, stopped the transformation. This experiment was crucial in establishing DNA as the molecule responsible for inheritance.
