What is an ORF ?

Open Reading Frame-

• It is a protein coding region consisting of the start codon and stop codon in DNA or RNA.
• Stop codon is absent in open reading frame of prokaryotes as it haults the progress of the reading frame.
• It comprises both the coding sequences exon and the non-coding sequences introns.
• In enkaryotes , long ORFs can continue over non-translatable intron gaps, so spliced mRNA must be employed to determine ORFs. Short ORFs can occur outside genes – within the intron, segments of DNA outside genes that were formerly considered ‘junk’ DNA. 
• A DNA open reading frame starts with ATG—coding for Met—in most species, and ends with a stop codon (TAA, TAG, or TGA).

Types of mutations in ORFs-

1.Nonsynonomous or mis-sense mutation 

2.Nonsense mutation

3.Synonomous or silent mutation 

4.Neutral non synonomous mutation 

5.Frameshift mutation (Deletion or insertion )

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