Question

Termination of polypeptide chain is brought by:
A. UUG
B. UAA
C. UUG
D. UCG

Answer 1

Hint: A polypeptide is an unbroken sequence of amino acids linked together by peptide bonds. The peptide bond attaches the carboxyl group of one amino acid to the amine group of its next amino acid to form an amide. Stop codons are used for the termination of polypeptide chains.

Complete Step by Step Answer:
The presence of any of the three termination codons, UAA, UAG, or UGA, causes the polypeptide chain to be terminated. One of the two release factors, RF1 or RF2, identifies these termination codons. UAA and UAG are identified by RF1, while UGA is acknowledged by RF2. They aid the ribosome in identifying these triplets. Seeing as suppressor tRNA is capable of acknowledging termination codons that can compete with release factors for admittance at the 'A' site, the release factors appear to act on it. A third release factor, RF3, appears to stimulate RF1 and RF2 activity. The polypeptide tRNA should be available on the 'P' site for the release reaction to occur, and the release factors aid in the separation of the carboxyl group in between polypeptide and the last tRNA handling this sequence. With the help of IF-3, the polypeptide is therefore released, and also the ribosome diffuses into two subunits.
Thus, within the given options, the correct answer is UAA as we know the other options are not termination codons.

Hence, the correct option is B

Note: Only one release factor, eRFI, is known in eukaryotic mechanisms. GTP appears to be required for this factor's adhesion to the ribosome. After the termination step, GTP is severed, which may be required for the discharge of eRFI from the ribosome.