Pre-mRNA

Definition

Pre-mRNA, or precursor messenger RNA, is the initial transcript produced from a gene during the process of transcription before it undergoes any processing. This molecule includes both introns and exons, meaning it contains non-coding and coding sequences that will be modified in later steps to produce mature mRNA. Pre-mRNA is essential for gene expression, as it represents the first stage of RNA synthesis that will eventually lead to protein production through translation.

5 Must Know Facts For Your Next Test

1. Pre-mRNA is synthesized directly from DNA during transcription and includes both exons and introns.
2. After transcription, pre-mRNA undergoes several modifications, including capping, polyadenylation, and splicing, to become mature mRNA.
3. Alternative splicing allows for different combinations of exons to be included in mature mRNA, leading to the production of multiple protein isoforms from a single gene.
4. The presence of introns in pre-mRNA is thought to facilitate evolutionary changes in genes by allowing for variations in splicing patterns.
5. Errors during the processing of pre-mRNA can lead to diseases or dysfunctional proteins due to incorrect mRNA or protein products.

Review Questions

• How does pre-mRNA contribute to the diversity of protein isoforms through alternative splicing?
  • Pre-mRNA contributes to protein diversity through the process of alternative splicing, where different combinations of exons are joined together while introns are removed. This means that a single gene can produce multiple mature mRNA transcripts that encode for various protein isoforms with potentially different functions. The ability to generate diverse proteins from a single pre-mRNA transcript is crucial for cellular function and adaptation.
• What role does splicing play in the maturation of pre-mRNA and how does it affect gene expression?
  • Splicing is a critical step in the maturation of pre-mRNA, as it removes non-coding introns and joins together coding exons. This process not only results in the formation of mature mRNA but also influences gene expression by determining which exons are included in the final transcript. The regulation of splicing can lead to the production of different protein isoforms from the same pre-mRNA, impacting cellular functions and responses.
• Evaluate the impact of defects in pre-mRNA processing on human health and disease.
  • Defects in pre-mRNA processing can have significant implications for human health, as they can lead to the production of faulty or non-functional proteins. For instance, mutations that affect splicing may result in the inclusion of introns or exclusion of critical exons in mature mRNA. Such errors can contribute to various diseases, including cancers and genetic disorders like spinal muscular atrophy. Understanding these defects highlights the importance of proper RNA processing mechanisms in maintaining cellular function and overall health.

Related terms

Intron: A non-coding sequence within a pre-mRNA that is removed during RNA processing before translation.

Exon: A coding sequence within a pre-mRNA that remains after introns are spliced out, contributing to the final mRNA molecule.

Splicing: The process by which introns are removed from pre-mRNA and exons are joined together to form mature mRNA.