開放閱讀框是基因序列的一部分，包含一段可以編碼蛋白的堿基序列，不能被終止子打斷。當一個新基因被識別，其DNA序列被解讀，人們仍舊無法搞清相應的蛋白序列是什麼。這是因為在沒有其它信息的前提下，DNA序列可以按六種框架閱讀和翻譯（每條鏈三種，對應三種不同的起始密碼子）。ORF識別包括檢測這六個閱讀框架并決定哪一個包含以啟動子和終止子為界限的DNA序列而其內部不包含啟動子或密碼子，符合這些條件的序列有可能對應一個真正的單一的基因產物。ORF的識別是證明一個新的DNA序列為特定的蛋白質編碼基因的部分或全部的先決條件。

    An open reading frame (ORF) is a portion of a gene’s sequence that contains a sequence of bases, uninterrupted by stop sequences, that could potentially encode a protein. When a new gene is identified and its DNA sequence deciphered, it is still unclear what its corresponding protein sequence is. This is because, in the absence of any other knowledge, the DNA sequence can be translated or read in six possible reading frames (three for each strand, corresponding to three different start positions for the first codon). ORF identification involves scanning each of the six reading frames and determining which one(s) contains a stretch of DNA sequence bounded by a start and stop codon, yet containing no start or stop codons within it; a sequence meeting these conditions could correspond to the actual single product of the gene. The identification of an ORF provides the first evidence that a new sequence of DNA is part or all of a gene encoding for a particular protein.