​Match the following bacterial gene expression mechanisms:​

​Which one of the following options represents all correct matches between Column X and Column Y?​

Correct option is D

EXPLANATION-

A. Translated protein acts as a repressor (translational feedback) - (ii) Ribosomal protein operon regulation

This refers to a mechanism where the translated protein itself regulates gene expression by acting as a repressor. This is a typical example of Ribosomal protein operon regulation where the ribosomal proteins regulate their own synthesis by feedback inhibition.

B. Production of ppGpp in response to amino acid starvation, which regulates transcription by binding to β subunit of RNA polymerase -  (i) Stringent response
This is a classic example of Stringent response, where ppGpp is synthesized during amino acid starvation and regulates transcription globally.

C. Regulation of bacterial mRNA translation in cis - (iv) Riboswitches that bind a ligand
In cis regulation, the regulatory element is present on the same molecule of mRNA being regulated. This typically involves Riboswitches that bind a ligand, affecting translation or transcription.

D. Regulation of bacterial mRNA translation in trans- (iii) sRNA (small RNA) and chaperone require pairing with mRNA.
Trans regulation involves small RNA molecules (sRNA) or proteins that regulate mRNA translation by pairing or interacting with the target mRNA.
So, this matches sRNA (small RNA) and chaperone require pairing with mRNA.

So the correct option is (d) - ​A (ii), B (i), C (iv), D (iii)
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