Final answer:
Uracil is the nitrogenous base that is not found within DNA; it is found in RNA, where it pairs with adenine. DNA contains adenine, guanine, cytosine, and thymine, and has specific base pairing rules.
Step-by-step explanation:
The component that is not found within DNA is uracil. DNA is composed of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Uracil (U) is instead found in RNA, where it pairs with adenine. This distinction is a fundamental difference between the two types of nucleic acids. The DNA structure is further stabilized by phosphodiester bonds and features complementary base pairing where adenine pairs with thymine and guanine pairs with cytosine. The relative amounts of these bases can vary by species but within a species, the amount of