Avery and DNA

Which result of Frederick Griffith’s experiments led him to believe in a “transforming principle”?

• Mice injected with live S bacteria died.

• Mice injected with live R bacteria lived.

• Mice injected with dead S bacteria lived.

• Mice injected with dead S and live R bacteria died.

An important factor in Oswald Avery’s ability to identify the “transforming principle” as DNA was the fact that proteins

• contain very little phosphorus.

• were present in the extract made from S bacteria.

• do not react with enzymes.

• could be observed in the extract made from R bacteria.

Chemical analysis of Avery’s extracts showed that the ratio of nitrogen to phosphorus was consistent with that of

• enzymes.

• DNA.

• protein.

• bacteria.

Hershey and Chase chose to use bacteriophages in their experiments because these viruses

• contain little more than DNA and protein.

• can be seen with a light microscope.

• can infect only bacteria, not humans.

• will not grow in radioactive culture.

As a result of the Hershey and Chase experiments, scientists believe that

• radioactive isotopes can be used safely.

• viruses use bacterial DNA to reproduce.

• the “transforming principle” is DNA.

• bacteriophages can be grown in culture medium.

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NGSS.HS-LS1-1