Exon: the portion of a pre-mRNAplugin-autotooltip__default plugin-autotooltip_bigpre-mRNA: In eukaryotes, genes are transcribed as a longer RNA molecule called pre-mRNA, which is then processed via splicing, 5'-capping, and 3' polyadenylation before it is transported into the cytoplasm and becomes a mature mRNA. that contains codonsplugin-autotooltip__default plugin-autotooltip_bigCodon: a three nucleotide sequence that is read by the ribosome and specifies an amino acid that is added to a growing poplypeptide chain based on the genetic code.. pre-mRNAsplugin-autotooltip__default plugin-autotooltip_bigpre-mRNA: In eukaryotes, genes are transcribed as a longer RNA molecule called pre-mRNA, which is then processed via splicing, 5'-capping, and 3' polyadenylation before it is transported into the cytoplasm and becomes a mature mRNA. usually contain multiple exons that are interspersed with intronsplugin-autotooltip__default plugin-autotooltip_bigIntron: sequences in a pre-mRNA that sit between exons and are removed by splicing. Formally speaking, introns are defined as being part of pre-mRNA, but the DNA sequence that codes for introns can also be informally described as introns.. Formally, exons are defined as a component of pre-mRNAplugin-autotooltip__default plugin-autotooltip_bigpre-mRNA: In eukaryotes, genes are transcribed as a longer RNA molecule called pre-mRNA, which is then processed via splicing, 5'-capping, and 3' polyadenylation before it is transported into the cytoplasm and becomes a mature mRNA., but the DNAplugin-autotooltip__default plugin-autotooltip_bigDNA: deoxyribonucleic acid. The genetic material for nearly all life on Earth. sequenceplugin-autotooltip__default plugin-autotooltip_bigSequence: the precise order of monomers in a polymer. In DNA, it refers to the order of G, A, T, and C nucleotides. In RNA, it refers to the order of G, A, U, and C nucleotides. In proteins, it refers to the order of amino acids. that codes for exons can also be informally referred to as exons.