Molecular Basis of Inheritance

Question

During protein synthesis in an organism at one point the process comes to a halt. Select the group of the three codons from the following, from which any one of the three could bring about this halt.

  • UUU, UCC, UAU

  • UUC, UUA, UAC

  • UAG, UGA, UAA 

  • UUG, UCA, UCG     

Answer

C.

UAG, UGA, UAA 

Non-sense codon or terminator codon are the codons that do not code for any amino acid. It is a set of three nucleotides for which there is no corresponding tRNA molecule to insert an amino acid into the polypeptide chain. Protein synthesis is hence terminated and the completed polypeptide released from the ribosome. Three stop codons are UAA (ochre), UAG (amber) and UGA (opal).

Mutations which generate any of these three codons in a position which normally contains a codon specifying an amino acid are known as nonsense mutations.

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