1944, what did he discover that DNA is responsible for

Biology: The Unity and Diversity of Life (MindTap Course List)
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Chapter8: Dna Structure And Function
Section: Chapter Questions
Problem 4DAA: HersheyChase Experiments The graph shown in FIGURE 8.5 is reproduced from an original 1952...
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In 1944, what did he discover that DNA is responsible for?
IV. Oswald Avery, McCarty and McLeod (Early 1940s)
After Griffith’'s experiment most scientists believed that the chemical transforming
bacteria was a protein, not a nucleic acid. Avery and his colleagues challenged that
assumption. Avery's work retested Griffith's hypothesis using a test tube assay in order to
determine which macromolecule was responsible for genetic information.
What molecule causes transformation? These experiments are extensions of Robert
Griffith's work.
Watch this for more help: https://www.youtube.com/watch?v=LPms5JQcwCA
Homogenize
cells
Centrifuge
Heat-kill
Recover IIIS filtrate
IIIS cells spun to
bottom of tube
Extract carbohydrates,
lipids, and proteins
IIIS cells in liquid
culture medium
Treat with
ribonuclease
Treat with
Treat with
protease
deoxyribonuclease
Assay for
Transformation
IIR cells
IIR cells
IIR cells
IIR cells
+
+
IIIS filtrate
RNase-treated
IIIS filtrate
DNase-treated
IIIS filtrate
Protease-treated
IIIS filtrate
No transformation
Transformation
Transformation
Transformation
occurs
occurs
occurs
occurs
IIR cells
IIR cells
IIR cells
Only IIR
cells
+
+
+
IIIS cells
IIIS cells
IIIS cells
Conclusion:
Active factor is not RNA
Conclusion:
Conclusion:
Active factor is
not protein
Control:
IIIS contains
active factor
Active factor is DNA
E IIIS cells
ESSA IIR cells
Transcribed Image Text:IV. Oswald Avery, McCarty and McLeod (Early 1940s) After Griffith’'s experiment most scientists believed that the chemical transforming bacteria was a protein, not a nucleic acid. Avery and his colleagues challenged that assumption. Avery's work retested Griffith's hypothesis using a test tube assay in order to determine which macromolecule was responsible for genetic information. What molecule causes transformation? These experiments are extensions of Robert Griffith's work. Watch this for more help: https://www.youtube.com/watch?v=LPms5JQcwCA Homogenize cells Centrifuge Heat-kill Recover IIIS filtrate IIIS cells spun to bottom of tube Extract carbohydrates, lipids, and proteins IIIS cells in liquid culture medium Treat with ribonuclease Treat with Treat with protease deoxyribonuclease Assay for Transformation IIR cells IIR cells IIR cells IIR cells + + IIIS filtrate RNase-treated IIIS filtrate DNase-treated IIIS filtrate Protease-treated IIIS filtrate No transformation Transformation Transformation Transformation occurs occurs occurs occurs IIR cells IIR cells IIR cells Only IIR cells + + + IIIS cells IIIS cells IIIS cells Conclusion: Active factor is not RNA Conclusion: Conclusion: Active factor is not protein Control: IIIS contains active factor Active factor is DNA E IIIS cells ESSA IIR cells
Expert Solution
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In the year 1928 Griffith made a remarkable discovery while working on pneumonia bacteria. He discovered that there was something that was capable of the transformation of bacterial cells from one strain to another. This bacteria had two physical forms, one was smooth surfaced another was rough-surfaced. Out of these two only smooth-type bacteria were able to cause pneumonia. During his experiment, he observed that when smooth strain bacteria that were killed by heating were mixed with rough-surfaced bacteria they were actually able to change into smooth-surfaced and cause pneumonia. He demonstrated his findings on mice and was successful. But Griffith was not able to actually propose that which molecule exactly caused the transformation and many researchers believed it to be protein after his discovery.

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