UNIT 4 4.1 DNA: THE MOLECULE OF LIFE TE 4.1 F EVALUATE , page 259 Answers: 1. Explain how Chargaff’s rules and Rosalind Franklin’s X-ray diffraction helped Watson and Crick discover the structure of DNA. Chargaff showed that the DNA nitrogen bases pair following the rule A-T and C-G. Rosalind Franklin’s X-ray diffraction showed that DNA was a double helix with the nitrogen bases on the inside of the molecule. The data from these two scientists helped Watson and Crick develop an accurate model of DNA . 2. Write the steps of replication in your own words. Make sure to use the following words in your explanation. DNA must be replicated in the nucleus so new cells have the correct amount of DNA to function. Enzymes unzip DNA and break the hydrogen bonds between the nitrogen bases . Free-floating nucleotides attach to the original strand using the base-pairing rule, creating a complementary strand . The result is two exact copies, each containing an original strand and a new strand. 3. C 4. D 5. C 6. B 7. C 8. A 9. D 10. D
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