Chapter 9: Problem 5

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, ribonuclease, and deoxyribonuclease, followed by the assay for retention or loss of transforming ability. What were the purpose and results of these experiments? What conclusions were drawn?

Short Answer

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Short Answer: Avery and his colleagues conducted experiments on the transforming principle derived from IIIS virulent cells, treating the fraction with proteases, ribonuclease, and deoxyribonuclease to determine which macromolecule was responsible for the transforming ability. The results showed that only the treatment with deoxyribonuclease eliminated the transforming ability, indicating DNA was responsible for the transformation. This conclusion provided crucial evidence that DNA is the genetic material and laid the foundation for understanding inheritance and gene expression in molecular biology.

Step by step solution

Understand the Transforming Principle

Avery and his colleagues aimed to identify the substance responsible for the transformation of non-virulent bacteria into virulent bacteria, known as the transforming principle. They obtained the transforming factor from IIIS virulent cells, and their goal was to determine the composition of this substance.

Explain the Treatments Applied to the Fraction

To identify the transformative factor, they treated the fraction with proteases, ribonuclease, and deoxyribonuclease. Proteases are enzymes that break down proteins, ribonuclease breaks down RNA, and deoxyribonuclease breaks down DNA. By treating the fraction with these enzymes, the researchers aimed to determine which macromolecules (protein, RNA, or DNA) were responsible for the transforming ability.

Discuss the Results of the Experiments

After treating the fractions with proteases and ribonuclease, the transforming ability was not affected, indicating that proteins and RNA were not responsible for the transformation. However, when the fraction was treated with deoxyribonuclease, the transforming ability was lost, suggesting that the substance responsible for the transformation was indeed DNA.

Conclusions Drawn from the Experiment

The results of these experiments led Avery and his colleagues to conclude that DNA is the transforming principle and the genetic material responsible for passing on heritable traits in living organisms. This breakthrough discovery laid the foundation for the field of molecular biology and contributed to the understanding of the role of DNA in inheritance and gene expression.

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Short Answer

Step by step solution

Understand the Transforming Principle

Explain the Treatments Applied to the Fraction

Discuss the Results of the Experiments

Conclusions Drawn from the Experiment

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