Pre-mRNA
The precursor mRNA or pre-mRNA is the primary transcript in the transcription process. It has both exons (coding sequence) and introns (non-coding sequence). Initially, it is produced from a DNA sequence inside the nucleus by transcription.
It undergoes many processing stages before being converted into mRNA or mature messenger RNA. The most important processing stage is RNA splicing, where the introns are removed. The other processing steps include 5’ capping and 3’ polyadenylation.
mRNA
mRNA is a single-stranded RNA that is created during transcription. It usually corresponds to the nucleic acid sequence of a gene. This mRNA sequence is translated by the ribosome into a protein. After the synthesis of protein, the mRNA degrades.
Structures in an mRNA
- The mRNA has coding regions beginning with the start codon and ending with the stop codon.
- They also have UTRs or untranslated regions before the start codon and after the stop codon. They maintain mRNA stability and also play a vital role in gene expression.
- There is a poly(A) tail (adenine sequence) added to the pre-mRNA sequence. This prevents the degradation of mRNA during gene expression.
Extended Reading: RNA Splicing – Process and Importance
Difference between Pre-mRNA and mRNA
Pre-mRNA |
mRNA |
|---|---|
|
It is a primary transcript that changes to mRNA. |
It is a single-stranded RNA created during transcription. |
|
It has both coding (exon) and non-coding (intron) sequences. |
It has only coding (exon) sequences. |
|
The pre-mRNA undergoes processing steps like – 5’ capping, RNA splicing and 3’ end polyadenylation. |
mRNA is a processed product. |
|
It does not travel to the cytoplasm. |
It travels to the cytoplasm to produce protein. |
Also Read: mRNA
Frequently Asked Questions on Difference between Pre-mRNA and mRNA
What is mRNA capping?
mRNA capping is vital to create a stable mRNA. This capping is done before the termination of the transcription process. The 5’cap is attached to the primary transcript, and it enhances the mRNA processing.
What is miRNA?
miRNA or microRNA is a single-stranded tiny RNA molecule that has a non-coding region. It has about 22 nucleotides. It usually functions within the mRNA sequence. Also, it plays a vital role in gene regulation.
What is RNA splicing?
It is a process where the pre-mRNA is transformed into mRNA or mature messenger RNA. This RNA splicing occurs in the nucleus. During this process, the introns or the non-coding regions are removed from the pre-mRNA. Also, this splicing leads to the ligation of coding regions or exons.
Also see: Stages of Transcription
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