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Chargaff's Rules quiz #3

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  • How did Chargaff's discoveries demonstrate that DNA base composition varies among species?
    Chargaff found that different species have different percentages of the four DNA bases (A, T, G, C), showing that DNA base composition is not the same across all organisms.
  • What was the first major discovery Erwin Chargaff made about DNA base composition?
    Chargaff discovered that DNA base composition varies among different species, meaning each species has different percentages of the four DNA bases.
  • According to Chargaff's second discovery, how do the percentages of adenine and thymine compare within a species?
    The percentages of adenine (A) and thymine (T) are roughly equal within a species.
  • What relationship did Chargaff find between guanine and cytosine in DNA?
    Chargaff found that the percentage of guanine (G) is roughly equal to the percentage of cytosine (C) in DNA.
  • Why are the percentages of A and T, and G and C, not exactly equal in Chargaff's data?
    The small differences are due to limitations in the experimental techniques Chargaff used at the time.
  • How did Chargaff's findings contribute to the understanding of DNA structure?
    His findings provided crucial evidence for complementary base pairing, which helped reveal the double helix structure of DNA.
  • What does it mean that DNA base composition varies among species?
    It means that different species have different proportions of adenine, thymine, guanine, and cytosine in their DNA.
  • How did Chargaff's rules challenge the previous assumption about DNA?
    They showed that DNA is not the same in all organisms, contradicting the earlier belief that DNA composition was uniform across species.
  • What is the significance of complementary base pairing in DNA?
    Complementary base pairing ensures that A pairs with T and G pairs with C, which is essential for accurate DNA replication and genetic information storage.
  • In the context of Chargaff's rules, what would you expect if a species has 31% adenine in its DNA?
    You would expect the species to have approximately 31% thymine, due to the roughly equal pairing of A and T.