Introns vs exons

Exons contain the actual genetic information coding for protein or functional RNA. Introns do not code for protein, but are important in regulation of gene expression. Different exons are frequently combined by alternative splicing to produce a larger number of unique proteins.

Introns are intervening sequences and stay in the nucleus, whereas exons exit and are expressed. Alternative splicing—can produce a variety of protein products from a single hnRNA (heterogeneous nuclear RNA) sequence (eg, transmembrane vs secreted Ig, tropomyosin variants in muscle, dopamine receptors in the brain, host defense evasion by tumor cells).

Visualizing Gene Expression: Transcription and Splicing

#boundingbox

This diagram illustrates the initial steps of gene expression. We start with a DNA sequence containing exons 1 through 6. This DNA is transcribed into heterogeneous nuclear RNA, or hnRNA, which includes both exons and introns. The hnRNA then undergoes splicing, where introns are removed. In the first example shown, exons 1, 2, 4, 5, and 6 are joined to form a mature messenger RNA, or mRNA, ready for protein translation.

Visualizing Alternative Splicing and Protein Diversity

#boundingbox

This part of the diagram showcases alternative splicing. From the same hnRNA, different combinations of exons can be selected. For instance, one mRNA might combine exons 1, 3, 5, and 6, while another uses exons 1, 4, 5, and 6. Each unique mRNA then undergoes translation, producing distinct protein structures, as shown by the varied protein models. This highlights how a single gene can yield multiple, functionally diverse proteins.

Topics Covered:

• Introns vs Exons: Basic Definitions
• The Role of Introns and Alternative Splicing
• Visualizing Gene Expression: Transcription and Splicing
• Visualizing Alternative Splicing and Protein Diversity