When Avery and his colleagues had obtained what was concluded to be the transforming factor from the IIIS virulent cells, they treated the fraction with proteases, RNase, and DNase, followed in each case by the assay for retention or loss of transforming ability. What were the purpose and results of these experiments? What conclusions were drawn?
Ch. 10 - DNA Structure and Analysis

Chapter 10, Problem 8
What observations are consistent with the conclusion that DNA serves as the genetic material in eukaryotes? List and discuss them.
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Step 1: Understand the historical context by recognizing that early experiments aimed to identify the molecule responsible for heredity, distinguishing DNA from proteins as the genetic material.
Step 2: Discuss the Avery-MacLeod-McCarty experiment, which showed that purified DNA from a virulent bacterial strain could transform a non-virulent strain, indicating DNA carries genetic information.
Step 3: Explain the Hershey-Chase experiment, where bacteriophages labeled with radioactive DNA and protein demonstrated that DNA, not protein, enters bacterial cells and directs viral replication.
Step 4: Describe observations in eukaryotes such as the correlation between DNA content and chromosome number, and the localization of DNA in the nucleus where genetic information is stored and transmitted.
Step 5: Highlight molecular evidence including the structure of DNA (double helix) and its ability to replicate accurately, supporting its role as the stable carrier of genetic information in eukaryotic cells.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Griffith's Transformation Experiment
This experiment demonstrated that a 'transforming principle' from dead virulent bacteria could genetically alter live non-virulent bacteria, suggesting the presence of a hereditary molecule. It laid the groundwork for identifying DNA as the genetic material.
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Transformation
Avery-MacLeod-McCarty Experiment
Building on Griffith's work, this experiment showed that DNA, not protein or RNA, was responsible for transformation in bacteria. By isolating DNA and demonstrating its ability to transfer genetic information, it provided strong evidence that DNA is the genetic material.
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Mendel's Experiments
Hershey-Chase Experiment
Using bacteriophages labeled with radioactive isotopes, this experiment showed that DNA, not protein, enters bacterial cells during infection and directs viral replication. This confirmed DNA as the genetic material in viruses, supporting its role in eukaryotes as well.
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Mendel's Experiments
Related Practice
Textbook Question
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Textbook Question
Why were ³²P and ³⁵S chosen for use in the Hershey–Chase experiment? Discuss the rationale and conclusions of this experiment.
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Textbook Question
Does the design of the Hershey–Chase experiment distinguish between DNA and RNA as the molecule serving as the genetic material? Why or why not?
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Textbook Question
What are the exceptions to the general rule that DNA is the genetic material in all organisms? What evidence supports these exceptions?
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Textbook Question
Draw the chemical structure of the three components of a nucleotide, and then link the three together. What atoms are removed from the structures when the linkages are formed?
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Textbook Question
How are the carbon and nitrogen atoms of the sugars, purines, and pyrimidines numbered?
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