Exons

Definition

Exons are the coding sequences of a gene that remain in the mature messenger RNA (mRNA) after the process of splicing has occurred. They are important because they dictate the amino acid sequence of proteins during translation and play a crucial role in eukaryotic transcriptional regulation by determining which parts of the gene are expressed in the final mRNA product.

5 Must Know Facts For Your Next Test

1. Exons can vary in length and number across different genes, leading to diverse protein products from a single gene through alternative splicing.
2. The splicing machinery, primarily composed of small nuclear ribonucleoproteins (snRNPs), recognizes specific sequences at the exon-intron boundaries to accurately remove introns.
3. In eukaryotic cells, exons are transcribed into pre-mRNA, which is then processed to remove introns before being translated into proteins.
4. Some exons can contain regulatory elements that influence gene expression and protein function, affecting how proteins interact with other cellular components.
5. The presence of exons allows for greater genetic diversity and adaptability by enabling organisms to fine-tune their protein production in response to environmental changes.

Review Questions

• How do exons contribute to the final protein product synthesized from a gene?
  • Exons are crucial for coding the amino acid sequence of proteins because they remain in the mature mRNA after splicing. During translation, the ribosome reads the sequence of exons in the mRNA to assemble amino acids into a polypeptide chain. This means that the composition and arrangement of exons directly affect the structure and function of the resulting protein, making them essential for proper gene expression.
• Discuss how alternative splicing impacts gene expression and protein diversity related to exons.
  • Alternative splicing allows for the inclusion or exclusion of specific exons from the final mRNA product, enabling a single gene to produce multiple protein variants. This increases the diversity of proteins that can be generated from a limited number of genes, allowing cells to adapt their functions according to different conditions. As a result, alternative splicing plays a key role in regulating gene expression and generating complexity in cellular functions.
• Evaluate the implications of errors in exon splicing on human health and disease.
  • Errors in exon splicing can lead to various health issues, including genetic disorders and cancer. For instance, if an exon is incorrectly included or excluded during splicing, it may result in nonfunctional or malfunctioning proteins that can disrupt normal cellular processes. This misregulation can contribute to diseases such as cystic fibrosis or certain types of cancer, highlighting the importance of accurate exon splicing in maintaining cellular health and function.

Related terms

Introns:

Introns are non-coding sequences within a gene that are removed during mRNA processing before translation.

Splicing: Splicing is the process by which introns are removed and exons are joined together to form a continuous coding sequence in mRNA.

Alternative Splicing: Alternative splicing is a regulatory mechanism that allows a single gene to produce multiple protein variants by including or excluding specific exons.