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Module 11 Lesson 1 Progress Check

Prompt

Read Lesson 1 (p.290-295) and complete "Check Your Progress" questions #2-4, 6

Response

  1. Describe the conclusions drawn by Hershey and Chase about the substance responsible for the transfer of genetic information.

    Hershey and Chase concluded that DNA is the substance responsible for the transfer of genetic information, not protein. They arrived at this conclusion by using bacteriophages tagged with radioactive isotopes of phosphorus and sulfur to infect bacteria. Radioactive phosphorus, found in DNA, was detected inside the bacteria, whereas radioactive sulfur, found in proteins, was not, demonstrating that DNA, not protein, carries genetic information.

  2. Describe the data used by Watson and Crick to determine the structure of DNA.

    Watson and Crick used Rosalind Franklin's X-ray diffraction images and Chargaff's rules of base pairing to deduce the structure of DNA. Franklin's images suggested a helical structure, while Chargaff's rules indicated how the bases pair across the two strands. These insights led them to propose the double helix model of DNA.

  3. Describe two characteristics that DNA needs to fulfill its role as a genetic material.

    DNA must be stable enough to reliably store genetic information and mutable enough to allow for evolution through genetic variations. Its stability ensures accurate replication and transmission across generations, while its mutability introduces the genetic diversity necessary for adaptation and evolution.

  4. Evaluate Hershey and Chase's decision to use radioactive phosphorus and sulfur for their experiments. Could they have used carbon or oxygen instead? Why or why not?

    Hershey and Chase's decision to use radioactive phosphorus and sulfur was strategic, as these elements are uniquely present in DNA and proteins, respectively. This allowed them to unequivocally determine that DNA was the genetic material. Carbon or oxygen wouldn't have worked because these elements are prevalent in all biomolecules, making it impossible to distinguish between DNA and proteins based on their radioactive labeling.