posttranscriptional processing RNA

[Jeff85]

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EK mentions that usually, one gene=1 polypeptide, except for postranscriptional processing RNA.
Why does that illustrate an exception?
(Isn't 1 polypeptide still being made even if phosphates or other molecules are posttranscriptionally added to the RNA portion?)

 

[loveoforganic]

Posttranscriptional modification extends beyond adding phosphates, methylating, etc. As one example, mRNA's can undergo splicing at various locations throughout the molecule that lead to different final mRNA's, that thus code different polypeptides. Thus, one gene -> one transcribed mRNA -> multiple posttranscriptional mRNA's -> multiple polypeptides.