Exons

Definition

Exons are the coding regions of a gene that are retained in the mature messenger RNA (mRNA) after the process of splicing. They play a crucial role in protein synthesis, as they contain the information necessary to produce specific proteins. In contrast to introns, which are non-coding regions removed during mRNA processing, exons are expressed and ultimately translated into amino acids during translation.

5 Must Know Facts For Your Next Test

1. Exons can vary greatly in size and number among different genes, leading to significant diversity in protein coding potential.
2. In eukaryotic cells, exons are typically separated by introns, while prokaryotic genes often lack introns altogether, meaning their coding sequences are contiguous.
3. Alternative splicing allows for a single gene to produce multiple proteins by including different combinations of exons in the final mRNA.
4. The presence of exons and the process of splicing contribute to post-transcriptional regulation, allowing cells to adapt protein production based on different needs.
5. Mutations within exons can lead to changes in the protein sequence, potentially resulting in functional differences or diseases.

Review Questions

• How do exons differ from introns in terms of their roles in gene expression?
  • Exons are the coding sequences that remain in the mature mRNA after splicing and directly contribute to protein synthesis. In contrast, introns are non-coding sequences that are transcribed into pre-mRNA but are removed before translation. This difference is fundamental in gene expression, as only exons provide the necessary information for building proteins, while introns serve no purpose in the final mRNA product.
• Discuss the implications of alternative splicing on protein diversity and cellular function.
  • Alternative splicing allows a single gene to generate multiple mRNA variants by including different combinations of exons. This leads to a diverse array of proteins being produced from one gene, which can enhance cellular function and adaptability. It is particularly important in complex organisms where tissue-specific protein isoforms may be required for specialized functions, demonstrating how alternative splicing contributes significantly to proteomic diversity.
• Evaluate the impact of mutations within exons on protein function and potential health outcomes.
  • Mutations within exons can directly alter the amino acid sequence of proteins, potentially changing their structure and function. Such changes can result in loss of function, gain of toxic function, or altered regulation of proteins, leading to various health issues or diseases. For instance, mutations causing misfolded proteins can be implicated in conditions like cystic fibrosis or certain cancers, highlighting the critical role that exonic integrity plays in maintaining proper biological functions.

Related terms

Introns:

Introns are non-coding segments of a gene that are transcribed into precursor mRNA but are removed during RNA splicing, thus not contributing to the final mRNA product.

Splicing: Splicing is the process by which introns are removed and exons are joined together in precursor mRNA to form mature mRNA, which is then translated into protein.

Precursor mRNA (pre-mRNA): Precursor mRNA is the initial transcript that contains both exons and introns and undergoes processing to become mature mRNA ready for translation.