which type of mutation stops the translation of the mrna?

A nonsense mutation stops the translation of mRNA.
This type of point mutation changes a codon that codes for an amino acid into a stop codon (UAA, UAG, or UGA), causing the ribosome to halt protein synthesis prematurely.

How Nonsense Mutations Work

Nonsense mutations occur when a single nucleotide substitution in DNA creates a premature termination codon in the mRNA sequence. During translation, ribosomes read mRNA until they encounter a stop codon, which signals release of the incomplete polypeptide chain. The resulting truncated protein is often non-functional, and the mRNA may undergo nonsense-mediated decay (NMD), further reducing protein production.

Comparison of Mutation Types

Mutation Type| Effect on Translation| Protein Outcome
---|---|---
Nonsense| Introduces premature stop codon 16| Truncated, usually non- functional 3
Missense| Changes one amino acid| Altered function possible 2
Silent| No amino acid change| No effect on protein 2
Frameshift| Insertion/deletion shifts reading frame| Garbled sequence downstream 4

Real-World Examples and Impacts

Imagine a gene for a vital enzyme: a nonsense mutation early in the sequence might produce a useless fragment, as seen in conditions like cystic fibrosis or Duchenne muscular dystrophy. Recent discussions (as of 2025 biology quizzes) highlight this in educational contexts, emphasizing its role in genetic diseases. Therapies like readthrough drugs aim to bypass these stops, allowing full translation.

TL;DR: Nonsense mutations create premature stop codons, halting mRNA translation and yielding incomplete proteins.

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