If the base-pairing in DNA becomes non-complementary such that purine bases can pair with one another and pyrimidine bases can pair with one another, the 1:1 ratio of purine to pyrimidine bases in DNA will no longer hold.
Due to the complementary base-pairing rule, the ratio of purine to pyrimidine bases in DNAs is usually 1:1. This is because Adenine always pairs with Thymine while Guanine always pairs with Cytosine.
Once this base-pairing rule is removed and becomes purine-purine and pyrimidine-pyrimidine pairings, then it becomes unnecessary for the ratio of purine to pyrimidine bases to be 1:1.
More on Chargaff's rule can be found here: https://brainly.com/question/19156457
