Reading frame

Definition

A reading frame is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) into a set of consecutive, non-overlapping triplets or codons. The correct reading frame determines which amino acids will be encoded by the gene.

5 Must Know Facts For Your Next Test

1. There are three possible reading frames in any given mRNA sequence.
2. Only one reading frame is translated into protein; this is known as the open reading frame (ORF).
3. Shifts in the reading frame, known as frameshift mutations, can result in completely different and usually nonfunctional proteins.
4. The start codon (AUG) establishes the correct reading frame for translation initiation.
5. Stop codons (UAA, UAG, UGA) terminate translation and define the end of an open reading frame.

Review Questions

• What establishes the correct reading frame for translation?
• How many possible reading frames exist for any given mRNA sequence?
• What can be the result of a frameshift mutation?

Related terms

Codon: A sequence of three nucleotides that together form a unit of genetic code in DNA or RNA.

Frameshift Mutation: A genetic mutation caused by indels (insertions or deletions) that change the grouping of nucleotides.

Open Reading Frame (ORF): A continuous stretch of codons that begins with a start codon and ends at a stop codon.