Open Reading Frames (ORFs)

Any given nucleotide sequence (single DNA strand or mRNA) can be interpreted in three possible ways, depending on where the coding starts. For example, the mRNA sequence ACCUUAGCGUA can be translated into Threonine-Leucine-Alanine ( $\underbrace{ACC}\underbrace{UUA}\underbrace{GCG}UA$), Proline-Stop-Arginine ( $A\underbrace{CCU}\underbrace{UAG}\underbrace{CGU}A$) or Leucine-Serine-Valine ( $AC\underbrace{CUU}\underbrace{AGC}\underbrace{GUA}$). These three ways are called reading frames. An open reading frame (ORF) is a sequence of codons with no stop codon.