Reading frame

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An example of three possible forward reading frames for a strand of DNA.
AGG·TGA·CAC·CGC·AAG·CCT·TAT·ATT·AGC
A·GGT·GAC·ACC·GCA·AGC·CTT·ATA·TTA·GC
AG·GTG·ACA·CCG·CAA·GCC·TTA·TAT·TAG·C

In

codons
.

A single strand of a

3′-end. These define the 5′→3′ direction. There are three reading frames that can be read in this 5′→3′ direction, each beginning from a different nucleotide in a triplet. In a double stranded nucleic acid, an additional three reading frames may be read from the other, complementary strand in the 5′→3′ direction along this strand. As the two strands of a double-stranded nucleic acid molecule are antiparallel, the 5′→3′ direction on the second strand corresponds to the 3′→5′ direction along the first strand.[1][2]

In general, at the most, one reading frame in a given section of a nucleic acid, is biologically relevant (open reading frame). Some viral transcripts can be translated using multiple, overlapping reading frames. There is one known example of overlapping reading frames in mammalian mitochondrial DNA: coding portions of genes for 2 subunits of ATPase overlap.

An example of a section of DNA translated by a computer in all six possible reading frames. The Open Reading Frames (ORFs) for Gene 1 and 2 are highlighted

Genetic code