7. DNA and Chromosome Structure

How were scientists able to determine that DNA, and not some other molecule, serves as the genetic material in bacteria and bacteriophages?

Explain why Avery, MacLeod, and McCarty's in vitro transformation experiment showed that DNA, but not RNA or protein, is the hereditary molecule.

Discuss the reasons proteins were generally favored over DNA as the genetic material before 1940. What was the role of the tetranucleotide hypothesis in this controversy?

Explain how the Hershey and Chase experiment identified DNA as the hereditary molecule.

Contrast the contributions made to an understanding of transformation by Griffith and by Avery and his colleagues.

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?

Given the state of knowledge at the time of the Avery, MacLeod, and McCarty experiment, why was it difficult for some scientists to accept that DNA is the carrier of genetic information?

Why were ³²P and ³⁵S chosen for use in the Hershey–Chase experiment? Discuss the rationale and conclusions of this experiment.

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?

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

What are the exceptions to the general rule that DNA is the genetic material in all organisms? What evidence supports these exceptions?

Describe the various characteristics of the Watson–Crick double-helix model for DNA.

What evidence did Watson and Crick have at their disposal in 1953? What was their approach in arriving at the structure of DNA?

How is the absorption of ultraviolet light by DNA and RNA important in the analysis of nucleic acids?

What is the physical state of DNA after it is heated and denatured?