Application Questions And Problems

17. A student mixes some heat-killed type IIS Streptococcus pneumonia bacteria with live type IIR bacteria and injects the mixture into a mouse. The mouse develops pneumonia and dies. The student recovers some type IIS bacteria from the dead mouse. It is the only experiment conducted by the student. Has the student demonstrated that transformation has taken place? What other explanations might explain the presence of the type IIS bacteria in the dead mouse?

*18. (a) Why did Hershey and Chase choose 32P and 35S for use in their experiment? (b) Could they have used radioactive isotopes of carbon (C) and oxygen (O) instead? Why or why not?

19. What results would you expect if the Hershey and Chase experiment were conducted on tobacco mosaic virus?

*20. Each nucleotide pair of a DNA double helix weighs about 1 X 10~21 g. The human body contains approximately 0.5 g of DNA. How many nucleotide pairs of DNA are in the human body? If you assume that all the DNA in human cells is in the B-DNA form, how far would the DNA reach if stretched end to end?

21. What aspects of its structure contribute to the stability of the DNA molecule? Why is RNA less stable than DNA?

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