Assertion :UAA, UAG and UGA terminate protein synthesis. Reason: They are not recognised by tRNA.
A
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
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B
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
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C
Assertion is correct but Reason is incorrect.
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D
Both Assertion and Reason are incorrect.
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Solution
The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion. Synthesis of polypeptide terminates when a non-sense codon of mRNA reaches the A-site. There are three non-sense codons; UAA, UAG and UGA. These codons are not recognised by any of the tRNAs. Therefore, no more aminoacyl-tRNA reaches the A site. The P-site tRNA is hydrolysed and the completed polypeptide is released in the presence of release factor. Hence, termination occurs.