Post-transcriptional modification is a process in cell biology by which, in eukararyotic cells, primary transcript RNA is converted into mature RNA. A notable example is the conversion of precursor messenger RNA into mature messenger RNA (mRNA), which includes splicing and occurs prior to protein synthesis. This process is vital for the correct translation of the genomes of eukaryotes as the human primary RNA transcript that is produced as a result of transcription contains both exons, which are coding sections of the primary RNA transcript.

In one allele (recessive) the transcriptional or post translational processes does not occur due to some modification and doesn't express while in other allele it occur (dominant).

Post translational modification occurs in ribosomes.

Before leaving the nucleus, the mRNA is modified (post-transcriptional modification). It is protected from ribonucleases by adding a 5' cap and a (3') poly A tail. These modifications help to stabilise the mRNA by preventing degradation by nucleases.

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