Any given sequence of DNA can therefore be read in six different ways: Three reading frames in one direction (starting at different nucleotides) and three in the opposite direction. During transcription, the RNA polymerase read the template DNA strand in the 3'→5' direction, but the mRNA is formed in the 5' to 3' direction.[4] The mRNA is single-stranded and therefore only contains three possible reading frames, of which only one is translated. The codons of the mRNA reading frame are translated in the 5'→3' direction into amino acids by a ribosome to produce a polypeptide chain.