Final answer:
Uracil is not found within DNA; instead, it is a nucleobase in RNA. DNA contains adenine, guanine, cytosine, and thymine. Adenine pairs with thymine, and guanine pairs with cytosine in DNA. Thus, the option D is the correct answer.
Step-by-step explanation:
The nucleobase that is NOT found in DNA is uracil. In DNA, the four nitrogenous bases are adenine, guanine, cytosine, and thymine. Uracil is the nitrogenous base that is found in RNA, where it pairs with adenine, taking the place of thymine from DNA. The statement that adenine binds to guanine is incorrect; instead, adenine pairs with thymine in DNA, and guanine pairs with cytosine, following the rule that purines always pair with pyrimidines. Furthermore, if we know that 30% of the bases in a DNA molecule are adenine due to complementary base pairing, the percentage of thymine will also be 30%.