5 Gene variant

Sometimes things can go wrong — one form of mutation

Thinking back to the formation of mRNA, if the bases at or near the sites of splicing are mutated in any way, splicing goes wrong. In this case, portions of RNA that do not code for a protein are left in the mRNA and, in all likelihood, the encoded protein will not be properly synthesised and will be degraded in the cell. In Figure 4 you can see an example of one such gene variant that alters splicing of exon 3 to exon 4. A single base change from G to A (indicated in the figure by *) leads to a shift in the position of mRNA processing by a single base. This variant is called the CYP2D6*4 (pronounced ‘star four’) variant and detecting it is one of the genetic tests you will be performing in this investigation.

Figure 4 A single base change can alter RNA splicing of the CYP2D6 gene © The Open University

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The diagram shows an example of a mutation, with the altered splicing of exon three to exon four. A single base change from G to A produces the variant CYP2D6 star 4.

Figure 4 A single base change can alter RNA splicing of the CYP2D6 gene © The Open University