DNA Biology Practice Test

Differential RNA processing through alternative splicing lets a single gene produce multiple protein isoforms by including or excluding certain exons during maturation of the mRNA. After transcription, the initial transcript is processed to remove introns and join exons, but sometimes specific exons are skipped in some transcripts. Skipping an exon means that part of the coding sequence is not included in the mature mRNA, so the produced protein has a different amino acid sequence and often a different function. This mechanism expands the variety of proteins a single gene can generate without changing the DNA sequence. Other options don’t fit this description because gene duplication creates extra copies of the gene rather than changing how a single transcript is processed; RNA editing tweaks individual nucleotides within the RNA without removing exons; and protein folding occurs after translation to shape the final three-dimensional structure, not to alter which exons are present in the protein-coding sequence.