Step 1: Understand DNA.
DNA (deoxyribonucleic acid) is the material that stores and passes on hereditary information in living things.
Step 2: List the DNA bases.
DNA contains four nitrogen bases: Adenine (A), Thymine (T), Guanine (G) and Cytosine (C).
Step 3: Recall the pairing rule.
In DNA the bases pair as A with T, and G with C. These pairs hold the two strands of the double helix together.
Step 4: Look at uracil.
Uracil (U) is not found in DNA. It is found in RNA, where it takes the place of thymine. In RNA, A pairs with U.
Step 5: Check the options.
Adenine, Cytosine and Thymine are all normal DNA bases. Only Uracil is missing from DNA.
Step 6: Conclude.
So the base that is NOT present in DNA is uracil.
\[ \boxed{\text{Uracil}} \]