Questions: What is the purpose of the mechanism of alternative splicing? It increases protein diversity.

The answer is the fourth one: It increases protein diversity.

Explanation for each option:

1. The function of alternative splicing is currently unknown.
   This is incorrect. The function of alternative splicing is well-studied and understood in the context of gene expression and protein diversity.

2. It allows rapid genetic evolution in bacteria.
   This is incorrect. Alternative splicing is a mechanism primarily observed in eukaryotes, not bacteria. Bacteria typically do not use alternative splicing as a means of genetic evolution.

3. It increases gene diversity.
   This is partially correct but not the best answer. While alternative splicing can lead to different mRNA transcripts from the same gene, it primarily affects the diversity of proteins rather than the genes themselves.

4. It increases protein diversity.
   This is correct. Alternative splicing allows a single gene to produce multiple protein isoforms by including or excluding certain exons during mRNA processing, thereby increasing the diversity of proteins that can be produced from a single gene.

In summary, the primary purpose of alternative splicing is to increase protein diversity, allowing organisms to produce a wide variety of proteins from a limited number of genes.