Reading frame

Reading frame is a concept in molecular biology that is used to explain how ribosomes translate mRNA sequences into proteins. It is a continuous sequence of codons, which are groups of three nucleotides that correspond to specific amino acids or stop signals during protein synthesis.

Overview

In the process of translation, the ribosome reads the mRNA sequence in a specific direction, from the 5' end to the 3' end. The reading frame that the ribosome uses to translate the mRNA into amino acids is determined by the start codon, which is usually the first AUG codon in the mRNA sequence.

There are three possible reading frames in an mRNA sequence, each starting from a different nucleotide in the first codon. The correct reading frame is the one that results in the production of a functional protein. If the ribosome starts translating at the wrong nucleotide, it will read the wrong codons, resulting in a non-functional protein.

Open reading frames

An open reading frame (ORF) is a sequence of DNA or RNA that has the potential to be translated into a protein. It starts with a start codon (AUG), and ends with a stop codon (UAA, UAG, or UGA). The length of an ORF is a multiple of three nucleotides, because each codon consists of three nucleotides.

ORFs are used in the process of gene prediction, where they are used to identify potential protein-coding regions in a DNA sequence. The presence of an ORF does not necessarily mean that it is expressed as a protein, as it could be a pseudogene or a non-coding RNA.

Frame shift mutation

A frame shift mutation is a type of mutation that changes the reading frame of the mRNA. This can occur through the insertion or deletion of nucleotides in the DNA sequence. If the number of inserted or deleted nucleotides is not a multiple of three, the reading frame will be shifted, resulting in the production of a different protein.

Frame shift mutations can have severe effects on the organism, as they can change the entire sequence of amino acids in the protein. This can result in a non-functional protein, or a protein with a completely different function.

See also

• Genetic code
• Codon
• Translation (biology)
• Mutation

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