Question

question 6 of 10
how did chargaff’s experiments affect the understanding of dna’s structure?
a. they revealed that each species has unique nitrogenous bases.
b. they led to the discovery that purines form base pairs with pyrimidines.
c. they showed the three - dimensional shape of a dna molecule.
d. they showed that dna is a polymer made of nucleotides.

Explanation:

Chargaff's experiments established two key rules: 1) the amount of adenine equals thymine, and guanine equals cytosine in DNA of a species; 2) base composition varies between species. This directly supported the idea that purines (adenine, guanine) pair with pyrimidines (thymine, cytosine), which was critical for the double helix model. Option A is incorrect because all species use the same four nitrogenous bases. Option C is incorrect as the 3D structure was discovered by Watson and Crick using X-ray data. Option D is incorrect because the understanding that DNA is a nucleotide polymer predated Chargaff's work.

Answer:

B. They led to the discovery that purines form base pairs with pyrimidines.