Intron

Definition

An intron is a non-coding segment of a gene that is transcribed into precursor mRNA but is spliced out before translation into protein. Introns play a crucial role in the regulation of gene expression and the evolution of genes, as they can harbor regulatory elements and provide space for alternative splicing, leading to the production of multiple protein isoforms from a single gene.

5 Must Know Facts For Your Next Test

1. Introns can vary widely in length, with some being just a few nucleotides long while others can be several kilobases long.
2. The presence of introns in eukaryotic genes contributes to the complexity of gene regulation and the ability to produce multiple protein variants from a single gene through alternative splicing.
3. Introns are thought to play a role in genetic diversity and evolution by allowing for recombination events that can lead to new gene functions.
4. Not all organisms have introns; prokaryotic genes typically do not contain introns, which makes eukaryotic gene structure unique.
5. The removal of introns occurs in the nucleus before the mature mRNA is transported to the cytoplasm for translation.

Review Questions

• How do introns contribute to gene expression regulation and protein diversity?
  • Introns contribute to gene expression regulation by providing regulatory sequences that can influence the transcription process. They also enable alternative splicing, allowing for a single gene to produce multiple mRNA variants, which results in diverse protein isoforms. This increases the functional versatility of proteins within cells, allowing organisms to adapt and respond to various environmental challenges.
• Compare and contrast introns and exons in terms of their roles in gene structure and function.
  • Introns are non-coding regions of a gene that are transcribed into precursor mRNA but are removed during RNA splicing, while exons are coding regions that remain in the mature mRNA and are translated into protein. The presence of introns allows for alternative splicing, increasing protein diversity, whereas exons determine the actual protein sequence. This distinction highlights how both introns and exons are essential for the complexity of gene function in eukaryotes.
• Evaluate the significance of introns in the evolution of eukaryotic organisms compared to prokaryotic organisms.
  • The presence of introns in eukaryotic genes is significant for evolution as it allows for greater genetic diversity through mechanisms like alternative splicing and recombination. In contrast, prokaryotic organisms generally lack introns, resulting in simpler gene structures. This difference underscores how introns may facilitate evolutionary innovations in eukaryotes by enabling more complex regulatory networks and adaptations, contributing to the vast diversity observed among eukaryotic life forms.

Related terms

exon:

An exon is a coding segment of a gene that remains in the mature mRNA after splicing and is translated into protein.

splicing:

Splicing is the process by which introns are removed and exons are joined together in precursor mRNA to form mature mRNA.

alternative splicing:

Alternative splicing is a regulated process during gene expression that results in a single gene producing multiple different mRNA variants, leading to diverse protein products.