Exons

Definition

Exons are the coding sequences of DNA that are transcribed into RNA and retained in the final mRNA molecule after splicing. They play a crucial role in the process of gene expression, as they provide the necessary information to produce proteins. In contrast to introns, which are non-coding sequences removed during RNA processing, exons are essential for translating genetic information into functional proteins.

5 Must Know Facts For Your Next Test

1. Exons can vary in size and can be present in different combinations within a gene, allowing for alternative splicing and the production of multiple protein isoforms from a single gene.
2. The number of exons in a gene can differ greatly between organisms, influencing the complexity of their proteomes.
3. During the transcription process, both exons and introns are initially transcribed into pre-mRNA, but only exons remain in the mature mRNA after splicing.
4. In eukaryotes, exons are often interspersed with introns within the same gene, while prokaryotic genes typically do not contain introns.
5. Mutations in exon sequences can directly affect protein structure and function, potentially leading to diseases or malfunctions within cellular processes.

Review Questions

• How do exons and introns differ in terms of their roles in gene expression?
  • Exons and introns serve very different functions in gene expression. Exons are the coding regions that contain the necessary information for producing proteins, while introns are non-coding regions that are removed during RNA processing. The presence of exons allows for the formation of a mature mRNA molecule that is ready for translation, whereas introns must be spliced out to prevent interference with protein synthesis.
• Discuss the importance of alternative splicing of exons in generating protein diversity.
  • Alternative splicing of exons is a crucial mechanism that increases protein diversity by allowing different combinations of exons to be included in the final mRNA transcript. This process enables a single gene to code for multiple protein variants, known as isoforms, each potentially having distinct functions. Such diversity is vital for cellular adaptation and specialization in response to various physiological conditions and developmental cues.
• Evaluate how mutations in exon sequences could impact protein function and lead to disease.
  • Mutations within exon sequences can have significant effects on protein function since they directly alter the amino acid sequence encoded by the mRNA. These changes can lead to malfunctioning proteins that may disrupt cellular processes and result in diseases. For example, mutations in exons can cause misfolded proteins or truncated versions that lack essential functional domains, contributing to various genetic disorders such as cystic fibrosis or certain cancers.

Related terms

Introns: Non-coding sequences of DNA that are transcribed into RNA but are removed during RNA processing before translation.

RNA Splicing: The process by which introns are removed and exons are joined together to form a mature mRNA molecule.

mRNA (messenger RNA): A type of RNA that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.