Open Reading Frame?

**sotellme** · Sep11-04, 01:42 PM

does anyone know what an ORF (open reading frame) is?

it would help me alot if anyone explains this to me.

thank you so much!

**iansmith** · Sep12-04, 02:15 PM

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.

http://www.geneed.com/glossary/o/index.html

The ORF definition has some small differences in bacteria and eukaryotes. Since bacteria have very few genes with introns, an ORF is usually the entire gene coding for a probable protein meaning there is a start codon and a stop codon and close the ORF, regulatory and stoping elements should be found. In bacteria you might also find several ORF close together and sometimes overlapping. This is an operon. In eukaryotes, ORF are usually the exons.

**sotellme** · Sep13-04, 08:27 AM

Originally Posted by iansmith

[url] In eukaryotes, ORF are usually the exons.

hello iansmith!

firstly i want to thank you for the great help! but i wonder how can ORF usually be an exon in eukaryotes? since as the definition says; an ORF should have both start and stop codon?

hope for reply!

thanks again!

**iansmith** · Sep13-04, 09:15 AM

an exon has a start and a stop sequence to mark the exon

**sotellme** · Sep13-04, 09:23 AM

Originally Posted by iansmith

an exon has a start and a stop sequence to mark the exon

uhh! this is something new to me

thanks alot!

**Monique** · Sep13-04, 10:35 AM

Those are splice sites.

An ORF is the reading frame from which DNA is translated into RNA. The initiation codon would be in the first exon and the termination codon in the last. The introns are not spliced out until after the transcription, so I think they do belong to the ORF.

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. Source : Celera