Question

Broad spectrum antibotics like streptomycin bind to smaller subunits of ribosomes of prokaryotes thereby

• A. Inhibiting protein synthesis
• B. Blocking action of peptidyl transferase
• C. Misleading of genetic code
• D. Causing point mutation

Answer 1

Answer: (C)

Misleading of genetic code

Any antibiotic, irrespective of its interaction with 30S or 50S ribosomal subunits, inhibit proteins synthesis; option A does not specify effect of binding to 30S subunit. Broad spectrum antibiotics, streptomycin and neomycin, are aminoglycosides that bind to sites on the 30S subunit and causes the misreading of genetic code that leads to abnormal proteins; thus they inhibit peptide initiation and elongation, option C is correct. Antibiotics that attach to sites on the 50S subunit prevents the formation of peptide bonds (chloramphenicol) or inhibits translocation of the subunit during translation (erythromycin); option B is incorrect. Point mutation is caused by changes in single nucleotide of gene; substitution, deletion or insertion of bases are responsible for point mutation. Binding of antibiotics to ribosomal subunits does not affect the gene structure; option D is incorrect. Option C is correct.