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Chapter 9: Problem 4

Contrast the various contributions made to our understanding of transformation by Griffith, Alloway, and Avery.

Short Answer

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Question: Briefly discuss the contributions of Griffith, Alloway, and Avery to our understanding of transformation in bacteria. Answer: Griffith's contribution was the discovery of the "transforming principle" in 1928, which showed that genetic information could be transferred between cells. Alloway's work enhanced the understanding of transformation by discovering "co-factors" that improved its efficiency. Avery, along with colleagues MacLeod and McCarty, identified DNA as the genetic material responsible for inheritance and transformation in bacteria in 1944. These contributions collectively shaped our knowledge of transformation and its role in bacterial evolution and adaptation.

Step by step solution

01

Introduction to Transformation

Transformation is a process in which a bacterial cell takes up and incorporates foreign DNA from its surroundings, leading to the acquisition of new genetic traits. This phenomenon plays a key role in bacterial evolution, adaptation, and virulence. Now, let's discuss the contributions of Griffith, Alloway, and Avery to our understanding of transformation.
02

Griffith's Contribution

Frederick Griffith was a British bacteriologist who conducted a famous experiment in 1928. He demonstrated that a harmless strain of Streptococcus pneumoniae (R strain) could acquire virulence (transforming into the S strain) by incorporating genetic material from the heat-killed virulent strain (S strain). This experiment showed that a "transforming principle" exists, which is responsible for the change in the bacterial phenotype. Griffith's work laid the foundation for the understanding of transformation and was the first evidence of the transfer of genetic information between cells.
03

Alloway's Contribution

David T. Alloway was an American microbiologist who worked on the enhancing substances of the transformation process. Alloway found that the efficiency of transformation could be significantly improved by the addition of heat-stable substances called "co-factors." His work provided further evidence for the existence of a "transforming principle" and contributed to the development of methodologies that allowed scientists to manipulate bacterial transformation more effectively.
04

Avery's Contribution

Oswald Avery was a Canadian-American physician and medical researcher who, along with his colleagues Colin MacLeod and Maclyn McCarty, identified the "transforming principle" as DNA in their 1944 experiment. They purified DNA from the S strain of Streptococcus pneumoniae and showed that it was sufficient to transform the R strain into the virulent S strain. Their work provided strong evidence that DNA is the genetic material responsible for inheritance and the transformation process in bacteria.
05

Conclusion

In conclusion, the various contributions made by Griffith, Alloway, and Avery led to our current understanding of transformation. Griffith's work was groundbreaking in that it first identified the existence of a "transforming principle," which was later enhanced by Alloway's discovery of co-factors that improved transformation efficiency. Finally, Avery's experiments solidified the concept that DNA is the genetic material responsible for this process. All these contributions have shaped our knowledge of the transformation process and its role in bacterial evolution and adaptation.

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Most popular questions from this chapter

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?

In this chapter, we have focused on DNA, the molecule that stores genetic information in all living things. In particular, we discussed its structure and delved into how we analyze this molecule. Based on your knowledge of these topics, answer several fundamental questions: (a) How were we able to determine that DNA, and not some other molecule, serves as the genetic material in bacteria, bacteriophages, and eukaryotes? (b) How do we know that the structure of DNA is in the form of a right-handed double-helical molecule? (c) How do we know that in DNA G pairs with C and that A pairs with T as complementary strands are formed? (d) How do we know that repetitive DNA sequences exist in eukaryotes?

What component of the nucleotide is responsible for the absorption of ultraviolet light? How is this technique important in the analysis of nucleic acids?

While demethylation can convert thymine to uracil, deamination can convert cytosine to uracil. Suppose these two mutations occur in a cell. What would be the impact on the DNA structure?

What observations are consistent with the conclusion that DNA serves as the genetic material in eukaryotes? List and discuss them.
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