Question

Alternative splicing is a common mechanism for eukaryotes to expand their repertoire of gene functions. At least one estimate indicates that approximately 50 percent of human genes use alternative splicing, and approximately 15 percent of diseasecausing mutations involve aberrant alternative splicing. Different tissues show remarkably different frequencies of alternative splicing, with the brain accounting for approximately 18 percent of such events. (a) Define alternative splicing and speculate on the evolutionary strategy alternative splicing offers to organisms. (b) Why might some tissues engage in more alternative splicing than others?

Short answer

Additionally, why might different tissues engage in varying levels of alternative splicing? Answer: Alternative splicing is a post-transcriptional process where different combinations of exons from a single pre-mRNA transcript are joined together, resulting in multiple protein isoforms from a single gene. As an evolutionary strategy, alternative splicing increases the functional diversity of proteins without requiring more genes, allowing organisms to have a more complex proteome and phenotype, which can improve their adaptability to different environmental conditions. Different tissues might engage in varying levels of alternative splicing depending on their functional requirements and complexity, with more complex tissues, such as the brain, often displaying higher levels of alternative splicing to generate a diverse array of protein isoforms that contribute to their specialized functions.

Step-by-step solution

Define Alternative Splicing

Alternative splicing is a post-transcriptional process in which different combinations of exons from a single pre-mRNA transcript can be joined together during mRNA processing, leading to the generation of multiple protein isoforms from a single gene.

Speculate on the Evolutionary Strategy

Alternative splicing provides several evolutionary advantages to organisms. By allowing different protein isoforms to be produced from a single gene, alternative splicing increases the functional diversity of proteins without the need for an increase in the number of genes. This enables organisms to have a more complex proteome and phenotype, which could enhance their ability to adapt to different environmental conditions and pressures. Now, let's address part (b) of the exercise.

Alternative Splicing in Different Tissues

Various tissues might engage in more alternative splicing than others due to the differences in their functional requirements and complexity. The frequency of alternative splicing is often related to the diversity of cell types and functions within a particular tissue. For example, the brain, which accounts for a significant percent of alternative splicing events, is an exceptionally complex organ with a variety of cell types and functions. The high level of alternative splicing allows the brain to produce multiple protein isoforms from a single gene, contributing to its functional diversity and facilitating complex processes such as neurogenesis, synaptic plasticity, and neurotransmission. In summary, alternative splicing is an important mechanism that allows cells to generate multiple protein isoforms from a single gene, contributing to protein diversity and enhancing an organism's ability to evolve and adapt. Different tissues engage in varying levels of alternative splicing depending on their functional complexity and requirements.