8.1 Identifying DNA as the Genetic Material

8.1 Identifying DNA as the Genetic Material
What did early scientist believe was the genetic material? Why?

8.1 Identifying DNA as the Genetic Material
What did early scientist believe was the genetic material? Why?
Proteins because they were more complex and not
DNA because they were TOO simple!

Experiments
Griffith’s experiment:
Results (Conclusion)

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Results (Conclusion)

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Live R bacteria – mice lived
Results (Conclusion)

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Live R bacteria – mice lived
Heat-killed S bacteria – mice lived
Results (Conclusion)

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Live R bacteria – mice lived
Heat-killed S bacteria – mice lived
Heat-killed S bacteria +
R bacteria = killed mice
Results (Conclusion)

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Live R bacteria – mice lived
Heat-killed S bacteria – mice lived
Results (Conclusion)
That some material must have been transferred from the heatkilled S bacteria to the live R bacteria!
Heat-killed S bacteria +
R bacteria = killed mice

Experiments
Griffith’s experiment:
Live S bacteria – killed mice
Live R bacteria – mice lived
Heat-killed S bacteria – mice lived
Results (Conclusion)
That some material must have been transferred from the heatkilled S bacteria to the live R bacteria!
He called the “mystery” material the “Transforming Principle.”
Heat-killed S bacteria +
R bacteria = killed mice

Avery’s experiment:

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:
 Protein extract + enzymes = transformation still occurred! (Death)

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:
 Protein extract + enzymes = transformation still occurred! (Death)
 RNA extract + enzymes
= transformation still occurred! (Death)

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:
 Protein extract + enzymes = transformation still occurred! (Death)
 RNA extract + enzymes
= transformation still occurred! (Death)
 DNA extract + enzymes
= transformation failed to occur!! (Lived)

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:
 Protein extract + enzymes = transformation still occurred! (Death)
 RNA extract + enzymes
= transformation still occurred! (Death)
 DNA extract + enzymes
= transformation failed to occur!! (Lived)
Because the enzymes broke down the protein, RNA, and DNA, and that only when the DNA was broke down with the enzymes did the mice survive (Lived)

Avery’s experiment:
Took extracts from S bacteria and combined them with R bacteria.
Their findings:
 Protein extract + enzymes = transformation still occurred! (Death)
 RNA extract + enzymes
= transformation still occurred! (Death)
 DNA extract + enzymes
= transformation failed to occur!! (Lived)
Because the enzymes broke down the protein, RNA, and DNA, and that only when the DNA was broke down with the enzymes did the mice survive (Lived); therefore, the DNA must be the transforming principle, or
GENETIC MATERIAL!

Hershey & Chase’s experiments:

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).
Proteins contain sulfur (S) and
DNA contains phosphorus (P).

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).
Proteins contain sulfur (S) and
DNA contains phosphorus (P).
Experiment 1: they “tagged” bacteriophage with radioactive sulfur and infected bacteria =
NO sulfur was found in the bacteria!

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).
Proteins contain sulfur (S) and
DNA contains phosphorus (P).
Experiment 1: they “tagged” bacteriophage with radioactive sulfur and infected bacteria =
NO sulfur was found in the bacteria!
Experiment 2: they “tagged” bacteriophage with radioactive phosphorus and infected bacteria = phosphorus was found in the bacteria!!!

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).
Proteins contain sulfur (S) and
DNA contains phosphorus (P).
Experiment 1: they “tagged” bacteriophage with radioactive sulfur and infected bacteria =
NO sulfur was found in the bacteria!
Experiment 2: they “tagged” bacteriophage with radioactive phosphorus and infected bacteria = phosphorus was found in the bacteria!!!
Concluded that the bacteriophages’ DNA had entered the bacteria, but the protein had not!

Hershey & Chase’s experiments:
Used bacteriophages (viruses that infect bacteria) because they were very simple
(contained only DNA surrounded by a protein coat).
Proteins contain sulfur (S) and
DNA contains phosphorus (P).
Experiment 1: they “tagged” bacteriophage with radioactive sulfur and infected bacteria =
NO sulfur was found in the bacteria!
Experiment 2: they “tagged” bacteriophage with radioactive phosphorus and infected bacteria = phosphorus was found in the bacteria!!!
Concluded that the bacteriophages’ DNA had entered the bacteria, but the protein had not!
Their findings convinced scientists that the genetic material is DNA and not proteins!!

What was “transformed” in
Griffith’s experiment?

What was “transformed” in
Griffith’s experiment?
Harmless R bacteria were transformed into pathogenic
(diseases causing) S bacteria!

Why was the bacteriophage an excellent choice for research to determine whether genes are made of
DNA or proteins?

Why was the bacteriophage an excellent choice for research to determine whether genes are made of
DNA or proteins?
Because bacteriophages are merely made up of a DNA molecule surrounded by a protein coat!

Why was the bacteriophage an excellent choice for research to determine whether genes are made of
DNA or proteins?
Because bacteriophages are merely made up of a DNA molecule surrounded by a protein coat! (Contain only DNA & protein)