What is the outcome of alternative splicing?

• A. A single mRNA transcript is produced.
• B. Different combinations of exons produce multiple mRNA transcripts and protein isoforms.
• C. All introns are kept intact in mature mRNA.
• D. Splicing occurs only in prokaryotes.

Answer: (B)

Alternative splicing lets a single gene create multiple mRNA transcripts by using different combinations of exons. During RNA processing, the cell can include or skip certain exons, or use different splice sites, so several distinct mature mRNAs arise from one gene. Those varying transcripts lead to different protein products, or isoforms, expanding the range of proteins the gene can produce. That’s why the outcome described is that different combinations of exons produce multiple mRNA transcripts and protein isoforms.

The other ideas don’t fit: producing only one mRNA ignores the variability introduced by alternative splicing; keeping all introns in mature mRNA isn’t how splicing works (introns are typically removed, with occasional intron retention as a special case); and splicing is a hallmark of eukaryotic gene expression, not something limited to prokaryotes.