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Molecular Basis of Inheritance
Mutations: Nonsense Mutation
1 question from 1 paper, each with its answer.
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Concepts tested
- Premature stop codon
All Questions
2003 AIPMT 1 question
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What would happen if in a gene encoding a polypeptide of 50 amino acids, 25th codon (UAU) is mutated to UAA : -UAU codes for the amino acid tyrosine, while UAA is a stop (termination) codon. Changing a sense codon into a stop codon is a nonsense mutation.
During translation, the ribosome reads codons 1 to 24 and adds 24 amino acids.
When it reaches codon 25, now UAA, no tRNA pairs with it. A release factor binds and translation stops, and the polypeptide is released.
The remaining codons (26 to 50) are not translated, and no second polypeptide is made, because translation cannot restart without a new start codon.
So a polypeptide of 24 amino acids will be formed.