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Open Reading Frame

A reading frame, in biology, consists of three-nucleotide codon sets in either DNA or RNA that are contiguous and non-overlapping. An open reading frame (ORF) is a similar sequence that can be translated into a protein or a polypeptide.

In any open reading frame, the start-code sequence or initiation codon that begins the protein is methionine ATG, and then stop-code sequence or termination codon ends it. The stop sequence is coded by what is termed a nonsense codon, or a codon that does not have an RNA match. There are only three nonsense codons: amber(UAG) ochre(UAA) and opal (UGA). As you can see, each one contains a "U" nucleotide, not normal to DNA.

Any time a geneticist finds a long open reading frame, it is an indication that there is probably a gene near it. Sometimes short open reading frames occur outside the genes, simply by chance, and these are generally examined and discarded. Open reading frames are crucial to genetic sequencing.

Web Resources On Open Reading Frame

ORF Finder
Open Reading Frames

Book Resources On Open Reading Frame

Functional Studies of E. Coli Ribosomes and Characterization of Mini Open Reading Frames by Vildan Dincbas
Molecular Biology of the Cell by Bruce Alberts et al

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