Question

"In 1944, Avery, Macleod, and McCarty provided direct evidence that DNA was the hereditary molecule. They treated heat-killed extracts from lethal SIII bacteria with various enzymes and found that transformation was prevented only upon treatment with _______."

Answer 1

DNases-deoxyribonucleaes.

Basically nucleotides in DNA molecules are held together in nucleic acids by the phosphodiester bonds.One of the enzymes which breaks these bonds down for degradation is DNases. They can be specific for degradation in a strand or both,. The breakdown can be from either 3' or 5' end of the strands.

Therefore, if DNase is the enzyme that degrade DNA, then its addition and catalysis in this investigation, should block the gene expression - mediating and coordinating action of DNA by degrading it .Therefore the failure of transformation of non-lethal to lethal bacteria must be due to inhibition of the actions of DNA in gene expression.

Consequently DNA is the actual molecule which caused gene expression and transformation in the bacteria and not protein present in the bacteria, since no transformation took place when its action was blocked by the enzyme.

Answer 2

Deoxyribonuclease (DNase)

Step-by-step explanation:

Deoxyribonuclease is an enzyme that degrades DNA by separating the phosphodiester bond that serves as the backbone of all DNA.

When the heat-killed extracts from lethal SIII bacteria was treated with DNase, transformation was prevented because the enzyme degraded the molecule that is responsible for transformation, that is the DNA.