Exon

Definition

An exon is a segment of a gene that contains coding information for proteins and is retained in the final mature messenger RNA (mRNA) after the process of RNA splicing. Exons play a critical role in determining the amino acid sequence of proteins, as they are the portions of the gene that will ultimately be translated into functional proteins. Their presence and arrangement in a gene can significantly impact gene expression and the resulting phenotype of an organism.

5 Must Know Facts For Your Next Test

1. Exons can vary in size and number among different genes, leading to diverse protein structures and functions.
2. Alternative splicing allows a single gene to produce multiple protein variants by including or excluding certain exons during mRNA processing.
3. The arrangement of exons can influence how genes are regulated, including their timing and level of expression.
4. Mutations within exons can have significant effects on protein function, potentially leading to diseases or altered traits.
5. Exons make up only a small portion of the total genomic DNA in higher organisms, with introns comprising the majority of the gene structure.

Review Questions

• How do exons and introns contribute to the process of gene expression?
  • Exons and introns work together to define the coding and non-coding regions of genes during gene expression. While exons contain the coding sequences that will be translated into proteins, introns are non-coding sequences that are removed during RNA splicing. This splicing process ensures that only exons are included in the final mRNA, allowing for precise protein synthesis. The interplay between exons and introns is essential for producing functional proteins and regulating gene expression.
• Discuss the significance of alternative splicing involving exons in generating protein diversity.
  • Alternative splicing is a crucial mechanism that enhances protein diversity by allowing different combinations of exons to be included or excluded from mature mRNA transcripts. This means that a single gene can give rise to multiple protein isoforms with potentially distinct functions, enabling organisms to adapt to varying environmental conditions or developmental stages. This versatility increases the complexity of proteomes and plays a vital role in cellular differentiation and function.
• Evaluate how mutations in exons can lead to phenotypic changes or diseases in organisms.
  • Mutations in exons can have profound effects on phenotypes by altering the amino acid sequence of proteins, potentially impacting their structure and function. For instance, a point mutation might result in a misfolded protein that cannot perform its intended role, leading to various diseases such as sickle cell anemia. Such alterations can disrupt biological processes, trigger abnormal signaling pathways, or impair cellular functions. Understanding these relationships highlights the importance of exons in both normal physiology and disease mechanisms.

Related terms

intron:

An intron is a non-coding segment of a gene that is transcribed into precursor mRNA but is removed during RNA splicing before translation into protein.

RNA splicing: RNA splicing is the process by which introns are removed and exons are joined together to form the mature mRNA that will be translated into protein.

gene expression:

Gene expression is the process by which information from a gene is used to synthesize a functional gene product, often a protein, impacting cellular function and organism traits.