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In Lederberg's replica plating experiment what shall be used to obtain streptomycin resistant strain : -
A
Minimal medium and streptomycin
B
Complete medium and streptomycin
C
Only minimal medium
D
Only complete medium
Detailed Solution
Lederberg and Lederberg grew bacteria on a master plate of complete medium (which supports all bacteria).
Using a velvet pad, they transferred (replicated) the colonies onto a plate of complete medium containing streptomycin.
Only colonies that were already resistant grew on the streptomycin plate, and the matching colonies on the master plate (never exposed to streptomycin) were also resistant.
This showed that resistance mutations arise spontaneously before exposure, and the antibiotic only selects them.
So complete medium and streptomycin are used to obtain the streptomycin resistant strain.
Using a velvet pad, they transferred (replicated) the colonies onto a plate of complete medium containing streptomycin.
Only colonies that were already resistant grew on the streptomycin plate, and the matching colonies on the master plate (never exposed to streptomycin) were also resistant.
This showed that resistance mutations arise spontaneously before exposure, and the antibiotic only selects them.
So complete medium and streptomycin are used to obtain the streptomycin resistant strain.