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A nonsense mutation introduces a premature stop codon, leading to an incomplete and nonfunctional protein.
Ref: NCERT Class 12 Biology Chapter 4: Principles of Inheritance and Variation Non-Mendelian Inheritance - Incomplete Dominance Co-dominance Multiple Alleles
Nonsense mutation introduces premature termination codon UAA, UAG, or UGA within open reading frame by single base substitution changing sense codon to stop. During elongation, release factor eRF1 recognizes stop codon leading to premature polypeptide release producing truncated protein often lacking critical domains. Transcripts containing early stop trigger nonsense-mediated mRNA decay reducing protein level. Such loss-of-function alleles frequently behave recessively and underlie many inherited diseases, including Duchenne muscular dystrophy nonsense variants requiring read-through therapeutic strategies. This principle illustrates essential molecular mechanisms governing replication fidelity and mutation fixation relevant for exam interpretation.
Ref: Lehninger Principles of Biochemistry, 8th ed., Chapter 27: Nonsense Mutation Premature Termination
