A point mutation is a type of mutation that occurs in DNA or RNA when a single nucleotide base is added, deleted, or changed. There are five different molecules that can make up nitrogenous bases on nucleotides: cytosine, guanine, adenine, thymine (in DNA), and uracil (in RNA). Point mutations can have various functional consequences, including changes in gene expression or alterations in encoded proteins. The effects of point mutations on the downstream protein product can range from no effect to deleterious effects, with regard to protein production, composition, and function. There are two types of point mutations: transition mutations and transversion mutations. Transition mutations occur when a pyrimidine base (i.e., thymine . At the level of translation, when RNA copied from DNA is converted into a string of amino acids during protein synthesis, point mutations often manifest as functional changes in the final protein product.