Tranversions are mutations that result in a change from a pyrimidine to a purine, or from a purine to a pyrimidine in deoxyribonucleic acid (DNA) or ribonucleic acid (RNA).

DNA nucleotides, each contain one of four nitrogenous (nitrogen containing) bases: adenine (A), thymine (T), guanine (G), and cytosine (C). RNA molecules contain uracil (U) in the place of thymine. In DNA, the pyrimidines, single-ring nitrogenous basic compounds, are cytosine and thymine. Because uracil substitutes for thymine in RNA, the pyrimidines in RNA are cytosine and uracil. For both DNA and RNA the purines, nitrogenous double-ringed basic compounds are adenine and guanine.

The bonding between DNA strands, or between an RNA molecule and a DNA strand, or between two RNA molecules is very specific. Adenine always bonds with thymine in DNA strands (A-T base pairing) or, in the alternative, adenine bonds with the substituting uracil in RNA molecules to...