What is splicing and what is the consequence of alternative splicing?

• A. Splicing adds introns to genes.
• B. Splicing removes introns and joins exons; alternative splicing produces multiple protein isoforms from one gene.
• C. Splicing changes DNA sequence.
• D. Splicing removes introns and joins exons; alternative splicing produces multiple protein isoforms from one gene.

Answer: (D)

Splicing is the RNA processing step where the noncoding introns are removed and the coding exons are joined together to make a mature messenger RNA. The consequence of alternative splicing is that the same gene can produce multiple distinct mRNA transcripts by including or excluding different exons, which leads to different protein isoforms from a single gene. This creates more protein variety without needing more genes. The other statements misstate what splicing does (adding introns or changing the DNA sequence) and don’t capture the way alternative splicing expands protein diversity.