Exons are the coding regions of a gene in eukaryotic DNA that remain in the mature messenger RNA (mRNA) after the process of RNA splicing. They are the sequences that actually get translated into proteins, distinguishing them from introns, which are non-coding segments removed during splicing.
🌍 Definition
- Exons: Segments of a gene that are expressed in the final mRNA and code for amino acids in proteins.
- Root: From “expressed region,” coined to contrast with introns (“intervening regions”).
🔑 Characteristics
- Coding Function: Exons contain sequences that specify amino acids in proteins.
- Splicing: During transcription, introns are cut out and exons are joined together to form continuous coding sequences.
- Alternative Splicing: Different combinations of exons can be joined, allowing one gene to produce multiple protein variants.
- Length & Number: Genes can have just a few exons or dozens, depending on complexity.
📚 Examples
- Human Hemoglobin Gene: Contains multiple exons that code for different parts of the hemoglobin protein.
- Dystrophin Gene: One of the largest human genes, with 79 exons. Mutations in specific exons can cause Duchenne muscular dystrophy.
- Alternative Splicing in Neurons: Exons are rearranged to produce diverse proteins critical for brain function.
🛠 Biological & Medical Significance
- Genetic Disorders: Mutations in exons can directly alter protein structure, leading to disease.
- Biotechnology: Exon sequencing is used in genetic testing and personalized medicine.
- Evolutionary Biology: Exon shuffling contributes to the evolution of new proteins.
- Medical Anthropology: Understanding exon variation helps explain population-level differences in disease susceptibility.
✨ Summary
Exons are the coding segments of genes that remain in mature mRNA and determine protein structure. They are central to gene expression, protein diversity, and medical genetics.
