The color wheel is made up of three different types of colors - Primary, Secondary, and Tertiary. The primary colors are red, yellow, and blue. They are called primary for a couple of reasons. First, no two colors can be mixed to create a primary color.
RNA contains uracil and DNA Thymine. RNA has five bases, but DNA only four. DNA contains a deoxyribose sugar, but RNA contains ribose sugar. DNA is a double strand of nucleotides, but RNA a single strand.
Accidental deamination may change the cytosine to uracil, or the methylated cytosine to thymine. Cytosine is one of four bases in DNA molecules. As shown in the above figure, it may be mutated to uracil by deamination. Since uracil is not part of DNA, this mutation can easily be detected and repaired by base excision. Suppose DNA, like RNA, were made up of uracil, then the cytosine to uracil mutation could be corrected only by mismatch repair which is very inefficient.