The base pair Uracil (U) is not found in DNA, but instead found in RNA. In DNA, Uracil is replaced by Thymine (T).

Here's why:

* DNA uses the four bases: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).

* RNA uses the four bases: Adenine (A), Guanine (G), Cytosine (C), and Uracil (U).

While Uracil and Thymine have very similar structures, they have different roles in the genetic code. Thymine's structure makes it more stable in the DNA molecule, while Uracil is more prone to degradation.