Question

Which of the following substances was used as a screening agent in the replica plating experiment?
A. Vitamin B12​
B. Cofactors and streptomycin
C. Amino acid lysine
D. Antibiotic streptomycin

Answer 1

Replica plating is a process that helps to inoculate a colony or number of clones on a separate plate in line with the numbered system. In each colony, various methods are checked, while holding the master plate from which the clones were selected.

Complete answer:
Joshua Lederberg and Esther Lederberg offer an experimental description of the genetic basis of adaptation. They both performed an investigation of bacteria to understand the genetic basis of evolution. They inoculated a dilute suspension of bacteria from an agar plate and obtained a master plate. They noticed that after some time, there were several different bacterial colonies in the master plate. Each colony that was formed through a repeated division from a single bacterium represents a clone.
Replica plating technology easily transfers colonies to several petri plates and is used for autotrophic detection. Joshua Lederberg & Esther Lederberg gave it. A colonial pattern that develops on the whole medium is marked by the inverted plating on the velveteen. Streptomycin sheets were pressed to move the impression on this master plate. Streptomycin-borne cells expand with streptomycin on the platform. The areas on the second plates in which colonies are not formed correspond to wild colonies without resistance to streptomycin on the original plate which is then used to separate mutant colonies and to multiply them.
Hence, the right answer is D- Antibiotic streptomycin.

Note: The replica plating experiment of Lederberg shows the genetic foundation of development since many colonies were able to survive in the presence of antibiotics and find resistance to penicillin. Penicillin-induced bacterial changes allow bacteria to grow in a new environment.