Final answer:
A set of 3 mRNA bases is called a codon, which specifies a particular amino acid for protein synthesis.
Step-by-step explanation:
A set of 3 mRNA bases is called a codon. Codons are consecutive sequences of three nucleotides on an mRNA molecule that correspond to a specific amino acid. With 64 possible combinations of adenine (A), uracil (U), guanine (G), and cytosine (C), each codon specifies a particular amino acid. For example, the mRNA codon GGU translates to the amino acid glycine, while GUC codes for valine. It's important to note that although each codon corresponds to one amino acid, some amino acids can be specified by more than one codon, allowing for the redundancy in the genetic code. Moreover, there are three stop codons that signal the end of protein synthesis.