The table below describes the effect of various antibiotics on protein translation in bacteria.

Column X		Column Y
Antibiotic		Mechanism of action
A.	Erythromycin	i. Binds to 235 rRNA in the 50S subunit of the ribosome
B.	Chloramphenicol	ii. Binds to 50S ribosomal subunit and inhibits elongation of peptide chain
C.	Tetracycline	iii. Binds to 30S ribosomal subunit interfering with binding of aminoacyl tRNA
D.	Streptomycin	iv. Binds to 16S rRNA in the 30S subunit of the ribosome

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

Correct option is A

Answer: (a) A–(i), B–(ii), C–(iii), D–(iv)

Explanation

Let’s match each antibiotic to its specific ribosomal binding site and mode of action:

A. Erythromycin → (i) Binds to 23S rRNA in the 50S subunit of the ribosome
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Erythromycin is a macrolide antibiotic.

It binds to the 23S rRNA within the 50S ribosomal subunit, blocking translocation of the growing peptide chain.
Correct.

B. Chloramphenicol → (ii) Binds to 50S ribosomal subunit and inhibits elongation of peptide chain

Chloramphenicol inhibits peptidyl transferase activity, preventing peptide bond formation.
Correct.

C. Tetracycline → (iii) Binds to 30S ribosomal subunit interfering with binding of aminoacyl-tRNA
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Tetracyclines block the A-site of the 30S subunit, preventing aminoacyl-tRNA attachment.
Correct.

D. Streptomycin → (iv) Binds to 16S rRNA in the 30S subunit of the ribosome

Streptomycin is an aminoglycoside.

It binds to 16S rRNA of the 30S subunit, causing misreading of mRNA and inhibition of initiation complex formation.
Correct.