Pre-mRNA

Definition

pre-mRNA, or precursor mRNA, is the initial RNA transcript produced during the process of gene expression. It is the unprocessed version of mRNA that undergoes several modifications before becoming the mature, functional mRNA molecule that will be used as a template for protein synthesis.

5 Must Know Facts For Your Next Test

1. pre-mRNA contains both coding (exons) and non-coding (introns) sequences, which must be processed to produce the mature mRNA.
2. The 5' end of pre-mRNA is capped with a modified guanine nucleotide to protect it from degradation and aid in translation initiation.
3. The 3' end of pre-mRNA is polyadenylated, with the addition of a poly(A) tail, which also helps stabilize the mRNA and facilitate export from the nucleus.
4. Splicing of pre-mRNA is carried out by a complex of small nuclear RNAs and proteins known as the spliceosome.
5. Alternative splicing of pre-mRNA allows for the production of multiple mRNA isoforms from a single gene, increasing the diversity of proteins that can be synthesized.

Review Questions

• Explain the role of pre-mRNA in the process of protein synthesis.
  • pre-mRNA is the initial RNA transcript produced during transcription, which is the first step of protein synthesis. It contains both coding (exons) and non-coding (introns) sequences. Through a series of processing steps, including splicing, capping, and polyadenylation, pre-mRNA is transformed into mature mRNA, which then serves as the template for the translation of proteins by ribosomes.
• Describe the modifications that pre-mRNA undergoes to become mature mRNA.
  • The pre-mRNA molecule undergoes several key modifications to become the mature, functional mRNA. These include: 1) The addition of a 5' cap, which protects the mRNA from degradation and aids in translation initiation. 2) The removal of non-coding intron sequences through the process of splicing, leaving only the coding exon sequences. 3) The addition of a 3' poly(A) tail, which also helps stabilize the mRNA and facilitate its export from the nucleus.
• Discuss the significance of alternative splicing of pre-mRNA and its impact on protein diversity.
  • Alternative splicing of pre-mRNA is a crucial process that allows for the production of multiple mRNA isoforms from a single gene. This increases the diversity of proteins that can be synthesized from a single genetic template. By selectively including or excluding different exons, the spliceosome can generate a variety of mRNA transcripts, each of which may be translated into a distinct protein with potentially different structures and functions. This flexibility in gene expression is essential for the complexity of higher eukaryotic organisms.

Related terms

Transcription:

The process of creating a complementary RNA strand from a DNA template, resulting in the production of pre-mRNA.

RNA Processing: The series of modifications that pre-mRNA undergoes, including splicing, capping, and polyadenylation, to become mature mRNA.

Splicing: The removal of non-coding intron sequences from pre-mRNA and the joining of coding exon sequences to create the final mRNA molecule.