Genetics Review

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Translation  ...from mRNA to protein Source:  image from the National Human Genome Research Institute (NHGRI) Genetic Illustrations. Definitions Translation is the process of translating the sequence of nucleotide bases in DNA/RNA into a sequence of amino acids in a protein. RNA contains four bases, and is used as the template for making proteins that are made from varying combinations of 20 amino acids. Amino acids are also called peptides or residues. A chain of amino acids is called a polypeptide. A codon is a set of three bases in a DNA or RNA sequence that specify a single amino acid. Each triplet codon codes for a specific amino acid. Some amino acids can be coded for by more than one triplet codon (i.e., the genetic code is degenerate). E.g., the triplet codons CTA, CTC, CTG, and CTT all code for the amino acid Leucine. Leucine can be abbreviated as Leu or L. The single letter representations are used in sequence database records. Also, notice that the first two letters of a triplet codon are usually the most important, and if an amino acid is coded for by more than one triplet codon, it is the last letter that varies.

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Revised September 29, 1999 Comments/questions about course to Renata Geer renata@ncbi.nlm.nih.gov Questions about NCBI resources to info@ncbi.nlm.nih.gov