Question

In a translational unit UTRs are present at :

• A. \( \text{5' end (after start codon) and 3' end (after stop codon).} \)
• B. \( \text{5' end (before start codon) and 3' end (before stop codon).} \)
• C. \( \text{5' end (after start codon) and 3' end (before stop codon).} \)
• D. \( \text{5' end (before start codon) and 3' end (after stop codon).} \)

Hint:

Visualize the structure of an mRNA: 5' UTR $\rightarrow$ Start Codon $\rightarrow$ Coding Sequence $\rightarrow$ Stop Codon $\rightarrow$ 3' UTR. The UTRs are non-coding regions that regulate translation.

Answer 1

The Correct Option is D

In a messenger RNA (mRNA) molecule, the translational unit is the region that is translated into a protein. This region is flanked by untranslated regions (UTRs) at both the 5' and 3' ends. The 5' UTR (5' untranslated region) is located at the 5' end of the mRNA before the start codon (AUG). It plays a role in ribosome binding and initiation of translation. The coding sequence, which contains the start codon and stop codon, is located between the 5' UTR and the 3' UTR. The 3' UTR (3' untranslated region) is located at the 3' end of the mRNA after the stop codon. It influences mRNA stability, polyadenylation, and translational efficiency. Therefore, UTRs are present at the 5' end (before the start codon) and the 3' end (after the stop codon) of a translational unit.