AAMC FL Practice Exam

Where does alternative splicing occur in the process of gene expression?

1. During protein synthesis

2. During DNA replication

3. During mRNA processing

4. During cellular respiration

The correct answer is: During mRNA processing

Alternative splicing takes place during mRNA processing, which is a critical step in gene expression. After transcription, the initial RNA transcript, or pre-mRNA, undergoes several processing steps before it can be translated into a protein. One of these steps is splicing, where non-coding regions called introns are removed, and coding sequences called exons are joined together. Alternative splicing refers to the process by which different combinations of exons are included or excluded from the final mRNA molecule, resulting in multiple possible mRNA variants from a single gene. This mechanism allows for the generation of diverse protein isoforms from a single gene, significantly increasing the functional diversity of the proteome. The other options are not relevant to the concept of alternative splicing. Protein synthesis occurs after mRNA processing, and thus does not involve splicing. DNA replication is the process by which DNA is copied, and it does not directly relate to mRNA processing. Cellular respiration concerns metabolic pathways that generate energy from substrates, which is entirely separate from gene expression and mRNA processing.