Which scientist is credited with the observation that guanine and cytosine occur in DNA in equal amounts?

Which scientist is credited with the observation that guanine and cytosine occur in DNA in equal amounts?

• A. Erwin Chargaff
• B. James Watson
• C. Rosalind Franklin
• D. Linus Pauling

Answer: (A)

The main idea is Chargaff’s rules: in DNA, guanine pairs with cytosine and adenine pairs with thymine, so their amounts are equal within a given organism. Erwin Chargaff observed that across many samples, the amount of G equals C and the amount of A equals T, though the overall base composition varies by species. This pattern suggested a specific pairing system and helped justify the uniform width and the complementary base-pairing model of the DNA double helix. Watson and Crick later built the actual structure using this principle, among other data. So the scientist credited with this observation is Erwin Chargaff.

The main idea is Chargaff’s rules: in DNA, guanine pairs with cytosine and adenine pairs with thymine, so their amounts are equal within a given organism. Erwin Chargaff observed that across many samples, the amount of G equals C and the amount of A equals T, though the overall base composition varies by species. This pattern suggested a specific pairing system and helped justify the uniform width and the complementary base-pairing model of the DNA double helix. Watson and Crick later built the actual structure using this principle, among other data. So the scientist credited with this observation is Erwin Chargaff.