Correct option is B
Correct Answer: (b)
Explanation: Upstream open reading frames (uORFs) generally act as negative regulators of translation of the main coding sequence. Ribosomes initiate translation at the uORF start codon, terminate there, and often dissociate before reaching the main ORF. Removing the start codon of the uORF prevents ribosome initiation at the uORF, allowing efficient scanning and initiation at the start codon of gene Y. This maximizes translation of gene Y.
Information Booster
· uORFs are common regulatory elements in eukaryotic mRNAs.
· Translation of a uORF reduces ribosome availability for the downstream main ORF.
· Ribosomal reinitiation after uORF translation is usually inefficient in yeast.
· Mutation or removal of uORF start codons enhances downstream gene expression.
· uORF-mediated regulation allows fine control of protein synthesis under stress conditions.
Additional Knowledge
The 5′ cap and poly(A) tail are essential for mRNA stability, nuclear export, and efficient translation initiation, so their removal would reduce, not increase, translation. Removing the uORF stop codon would extend translation into downstream regions and likely interfere with normal gene Y translation. Therefore, specifically eliminating the start codon of the uORF is the most effective strategy to maximize translation of gene Y.
