Question

To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _______. To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _______.

Answer 1

Used the complete extract to incubate nonvirulent cells

Step-by-step explanation:

Avery and his colleagues injected the extracts from a virulent strain of Streptococcus pneumoniae into the mice and observed that the mice died. They extracted the DNA from the heat-killed virulent strain of Streptococcus pneumoniae. RNAse and proteases enzymes were used to remove the RNA and proteins present in the extract.

This was followed by incubation of mice with DNA extract of virulent heat-killed bacteria and the live non-virulent strain to show that the DNA from heat-killed virulent strain transformed the live non-virulent strain to the virulent one. This was why the mice died of the infection.

However, to ensure that the DNA was present in the virulent cells, they used the complete extract from virulent bacteria without any treatment with RNAse and proteases to transform the nonvirulent cell. It was proved that the DNA was the genetic material for transformation.